An eventful day for Monty who went from the best-placed Briton to looking like he was set for an early return ticket home.
A bogey on the last has sent him to five over. The cut was projected at four over. But with the top 60 and ties making the weekend five over will make it.
So he will ride again tomorrow, and so will we.
We go again to bring you all the news from Chambers Bay, this time with added BBC Radio 5 live commentary.
See you there.
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Henrik Stenson signs off on an underwhelming four-over round to finish only one under overall.
Meanwhile Colin Mongomerie is backed right up to the wall. The Scot is four over. Those on five over look set to miss out.
He is on that crazily-steep par three ninth.
Latest scores
-5 Spieth (US) F, Reed (US) F, -4 Grace (SA) F, D Johnson (US) F -3: Luiten (Ned) F, Finau (US) F, Summerhays (US) F, Martin (US) F
Selected others +1 P Casey (Eng) F: +2 Westwood (Eng) F; Rose (Eng) F; +3: Mickelson (US) F +4 Donald (Eng) F,McIlroy (NI) F, Montgomerie (Sco) 17, +5 Poulter (Eng) F +16 Woods (US) F
The ball pauses on the edge, looked down the manhole and decided it didn't want to get subterranean.
Patrick Reed had to put up with a bogey on the last - but he still has a share of the lead to look at.
Jordan Speight and Dustin Johnson are also at the top of the pops.
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Patrick Reed headed to the seaside on the last. No time for that, there is a halfway stage lead to wrap up.
Up and out to the green a very faint chance of a birdie. Deep consultation with the caddy, but what does he know? The ball dribbles into no man's land. Still work to do.
McIlroy slips to +4
Rory McIlroy's teasing round - hinting at a revival, posturing for a charge - has crashed and burned with three dropped shots in the final two holes.
After the double bogey on 17, comes a bogey on 18, leaving him high, dry and handsome on four over.
He is just one shot the right side of the cut-off line as it stands.
Johnson back to -3
Dustin Johnson's creaky final few holes culminates in a bogey on 18. He left a fair few shots out that and could be clear of the rest.
As it is, three bogies in the last four holes leave him four under par and one over for today. He is two shots off Patrick Reed and one behind Jordan Spieth on the leaderboard.
McIlroy slips to +3
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Never mind the wheels, the wingmirrors, axel and engine have dropped out off Rory McIlroy's round on 17.
The Northern Irishman had chiselled and clawed his way back to a decent score over a matter of hours, and has now chucked it in the bin in minutes.
A three-putt back from that heavy-handed second shot means he cards a double-bogey five on 17.
He is a distant three over overall.
Day update
A further update on Jason Day, who collapsed on the ninth hole earlier today,from his agent Bud Martin: "Jason was diagnosed to have suffered from Benign Positional Vertigo. He was treated locally by Dr. Robert Stoecker and Dr. Charles Souliere and is resting comfortably.
"His condition is being monitored closely and he is hopeful he will be able to compete this weekend in the final rounds of the US Open. He wants to thank all who treated him at the Franciscan Medical Group and thank all of the fans and friends who have reached out to he and his family."
Reed moves into sole lead at -6
Patrick Reed is still dead-eyed and zoomed in on the prize though.
The American taps in his birdie putt on 16 and marches off to the two final holes with a seven-under lead to lord over everyone else in the field.
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Rory McIlroy's hands are heavy as lead on 17, clumping the ball almost through the back of the green.
He has given himself loads to do here. A good 15 yards to make up on the return trip.
Concentration is fraying among these last starters.
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At the top of the leaderboard, it is Patrick Reed who is the coming force.
He feathers a delicious second shot up to within four feet on 16 just as Dustin Johnson yanks his drive right on the last.
Exclusive hold of the lead is surely in the post already.
Latest scores
-5 Spieth (US) F, Reed (US) 15, D Johnson (US) 17-4 Grace (SA) F. -3: Luiten (Ned) F, Finau (US) F, Summerhays (US) F, Martin (US) F
Selected others +1 P Casey (Eng) F: McIlroy (NI) 16 +2 Westwood (Eng) F; Rose (Eng) F; +3: Montgomerie (Sco) 15, Mickelson (US) F +4 Donald (Eng) F, +5 Poulter (Eng) F +16 Woods (US) F
Within moments of each other, the joint leaders Dustin Johnson and Patrick Reed both slip back into the clutches of the clubhouse leader Jordan Spieth.
Their dropped shots on 17 and 15 respectively means it is a three way carve-up at the top of the leaderboard.
McIlroy stays on +1
Rory McIlroy zinged his drive on the par-four 16, but he misses with his birdie putt and stays in positive figures.
Meanwhile a train clatters through on the tracks adjacent to the green.
Not Hammer's time
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Fifteen-year-old Cole Hammer is in the last group out on the course.
The third-youngest player ever to compete at the US Open, and so far it has been a learning experience at best for the Houston-based amateur.
He is nine over for today after a triple -bogey seven on 11.
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Putt wobbling all over a sun-baked rough-cut green?
Rory McIlroy with a par that feels like a birdie or better.
He looked like he was on the hook on 13 after a horrible drive put him in the rough. But a fine recovery up and down - the second half a nerveless putt downhill - means the eagle he picked up on the previous hole is unscathed.
Mickelson to +4 and outside cut
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Phil Mickelson's wait for a first US Open title will stretch out for to at least a 26th year as it stands.
The six-time runner-up has chalked up a second straight bogey - dropping a shot at seven - to slip to four over and outside the projected cut.
He has two more holes to haul himself, coughing and spluttering into the weekend.
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Rory McIlroy is in a world of pain on 13.
A punt out of the rough followed by an undercooked third leave him with an a very difficult up-and-down from below the level of the green just to make bogey...
Reed to -7 and share of lead
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Say what you want about him, and plenty do, but Patrick Reed is brimful of fighting spirit and self-belief.
He knocks in an eagle putt on 12 and is back into a share of the lead.
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"Pick up another shot over his final six holes and Rory McIlroy will be at level par at the halfway stage. A great platform for a challenge with 36 holes to play and a fair wind behind him. He could, he just might, be involved in the Sunday shakedown."
Woah, hold your horses. There are a lot of ifs and buts in there and that is even before McIlroy fades his drive off the 13th tee, wide of the 105-yard landing strip and into the rough.
Reed back to -5, McIlroy to +1
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Did the leaderboard move for you? It did for me.
Patrick Reed is straight back on the horse, teasing in a birdie putt on the 10th to return to -5 and a share of second.
Meanwhile Rory McIlroy finally sinks a putt for an eagle two on the 12th. That is him moving on up to +1.
Fun and games
Want to get an idea of the big-dipper greens at Chambers Bay?
This video, on Ian Poulter's Facebook page, is for you. The Englishman turns a one-foot putt into a three-footer via a 450-foot detour up and down a huge slope behind the hole
Reed back to -4
Patrick Reed had sole ownership of the lead an hour or so ago, but has come off the boil since. His third bogey in four holes takes him out to four under and only, only, a share of third.
Mickelson slips to +3
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Phil Mickelson very nearly saves his skin with a marathon putt on the sixth, but it runs around the rim and stays out.
He is rapidly heading the wrong way.
Projected cut now at +4
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The projected cut has gone out from three over to four over.
That means a reprieve for England's Luke Donald and Spanish sea dog Miguel Angel Jimenez as well.
The other five are none too shabby either: Craig Wood in 1941, Ben Hogan 1953, Arnold Palmer 1960, Jack Nicklaus 1972 and Tiger Woods in 2002.
Johnson to -7 and two-shot lead
Dustin Johnson slides his birdie putt right down the gullet of the 11th hole.
His advantage over the field and nearest challengers Patrick Reed and Jordan Spieth is up to two shots.
A red, white and blue look to the leaderboard and it is nothing to do with the Union Jack.
Eight of the top 12 are American.
Mickelson stays at +2
Ol' Lefty Phil Mickelson would surely be the most popular winner with the local punters up in the Pacific North West.
The American five-time Major winner has a birdie putt at the par-four fifth. But again it undercooked. He stays two over with four holes left on his card.
Reed back to -5
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Patrick Reed drops back with a bogey on the ninth, to leave Dustin Johnson alone at the top of the leaderboard.
Rory McIlory goes limp-wristed over an uphill birdie putt on the 10th green. "Not up, not in." And that is neither. The whole field have been struggling with that putt. Give it some welly lads.
Stenson back to -4
Henrik Stenson marks his arrival on the front nine (he started on hole 10) with a birdie four.
The Swede is back to four under and a share of fourth place with South Africa Branden Grace
Better.
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Apparently Sergio Garcia is copping a bit of heat from some of the spectators after his less-than-complimentary comments about the greens yesterday.
He said they were "as bad as they look" after the first round. And they do look like your local municipal links after the greenkeeper mixed-up the weedkiller wrong.
"If my problem is saying what everyone thinks but they don't have the guts to say it, then I'm guilty of that for sure," added Garcia yesterday.
The Spaniard is two over for the round, putting him two over overall.
Reed into share of lead at -6
Patrick Reed comes off the eighth green - like some sort of Escher drawing, all deceptive slopes and red herrings - with a birdie.
Dustin Johnson has a chance to immediately re-establish his lead on the ninth, but his own birdie putt lacks legs.
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Nothing like the spontaneous expression of joy and fraternal love that is a high-five is there?
McIlroy still on +3
Rory McIlroy has a 10-foot birdie putt after safely making it down onto the dancefloor from the elevated tee on the par-three ninth.
Nothing is dropping for him today though. The ball stays north and his score stays on the high side as well.
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Patrick Reed has practically got a theodolite and set square out to measure up a mammoth eagle putt on the par five. Drain this and he is leading solo.
It is a risky one though, heading downhill. He gives it a tickle and even that was a bit heavy. He has six feet to negotiate back up the hill.
Johnson back to -6
Dustin Johnson's momentum is checked with a bogey four on the ninth.
He is still at the top of the tree though on six under. His lead over Ryder Cup compadres Jordan Spieth and Patrick Reed is down to one shot though as rounds the turn.
He is solid and secure off the 10th tee
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By the way, Dustin Johnson has the whole clan over to watch this charge at the top of the leaderboard.
Wife Paulina Gretzky, son Tatum and father-in-law Wayne are all at Chambers Bay.
If Tatum doesn't live out the plot of Happy Gimore with Dustin Johnson as his dad and Wayne Gretzky's daughter as his mum, there is no hope..
McIlroy stays +3
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Rory McIlroy with a long look at a long-range birdie putt on the par-five eighth.
He might as well have been trying to read Ancient Greek as that green. The ball stayed stubbornly out left, refusing to break as he thought it might.
A frustrating day continues.
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Cheers Peter.
Rory McIlroy's indifferent form at least takes him out of the thorny "best-placed Brit" issue.
That honour is currently held by Marc Warren of Scotland on one under through seven, with Paul Casey, one over and done for his day, his nearest competition.
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Dustin Johnson on the par-three ninth. And he's in the sand. One yard from perfection.
Back on the eighth and Rory McIlroy is chipping his third from short of the green. It hops and skips and comes to rest 15 feet from the pin. If ever he needed a birdie.
Perhaps Mike Henson can bring him more luck than I. Let's find out...
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That's three birdies in five holes for Dustin Johnson on some of the hardest holes on the course. Sergio Garcia, by contrast, has shipped three in the last four.
Scotland's Marc Warren is fighting hard. A birdie on the 15th has got him back to one under for the tournament.
Johnson leads on his own
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Big swing at the top of the leaderboard.
Dustin Johnson gets all aggressive with his eagle putt on the eighth but trundles in for birdie from five feet to get to seven under.
Patrick Reed pays the ultimate penalty for missing the fairway on the seventh. His third from the back of the green gets diverted by on a huge slope and the par putt stays up. He drops back to five under, level with Jordan Spieth.
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Sergio Garcia's decent start is in danger of unravelling. A bogey on the seventh and he's just raced a birdie putt on the eighth six feet past and his putting woes continue. The Spaniard suddenly out to +2.
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Patrick Reed has no cut pressures at the moment but he is playing to the seventh green out of the claggy rough to the left of the fairway. He can't hold the green and has a tricky up and down for par.
Colin Montgomerie gives himself a chance of picking up a shot on the par-three 17th with a decent tee shot into the guts of the green.
McIlroy under pressure
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Rory McIlroy is in danger of missing the cut. His birdie putt from the back of the seventh green leaves him a dozen feet for par. But he's not making that and the world number one is right on the cut line at +3.
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Bubba Watson eyes up the bunker shot on the second and flies it way up into the air. It lands softly but he's got work to do for par.
On the seventh, Martin Kaymer's defence could be ending today. He doesn't borrow enough on a lengthy birdie putt and misses the 15-foot par putt that follows. He's back to +4.
Dustin Johnson finds the par-five eighth green in two. A 25-footer for eagle.
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Bubba Watson with a wild swish from the rough on the second and he is heading into a greenside bunker. He is +3 and on the cut mark.
Rory McIlroy smashed his drive down the seventh into Dustin Johnson country but he cannot match the American's accuracy with a wedge in his hand. His ball skips over the mound that Dustin's rolled back down towards the hole. Instead of a three-foot putt, Rors is facing a 40-foot birdie attempt.
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Niall: Dreams of Monty and Speith being paired together in the final round. Thirty years/stone between them, neck and neck going down the home stretch.
Dustin back on top
Back to the seventh for Dustin Johnson's birdie attempt. I did him a disservice. His approach finished three feet from the pin. A much easier putt and Dustin duly obliges to join Patrick Reed as US Open leader on six under par.
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Patrick Reed crouches down behind his birdie putt on the sixth. It's similar to the one Rory McIlroy just missed, maybe a touch longer and he misses to the right, just like Rory.
Sergio Garcia, never the greatest putter in the world, is a touch short with a birdie putt on seven but he is level for the round and tournament and hanging in there.
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Lee Westwood on Twitter: Played great today. Shame about 18. I know I made triple but it's a stupid par 4 and a great par 5. Sun and wind on this golf course all day. Chambers Bay will be brutal this afternoon. Great viewing.
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Dustin Johnson takes full advantage of his monster drive on the seventh. His short iron stops abruptly and then dribbles back towards the hole leaving a six-foot birdie putt.
Phil Mickelson misses a birdie opportunity on the par-five first but is in for par to stay +2.
Henrik Stenson's putting radar is also slightly off but he stops the rot of successive bogeys with a par on the 16th to stay three under.
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Rory McIlroy's birdie putt on the sixth races a couple of feet past but he has more nerve than Monty and holes out. Back down the fairway, Patrick Reed hits his approach pin high but he's 30 feet left of the pin.
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Monty for birdie on 15 from 20 feet and that's meandering right, a testy couple of feet for par. And he's tugged that left. A three-putt bogey and a third successive bogey sees the Scot back to one over par.
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James Bamford: Well done @usopengolf taking the pros out of their comfort zone and challenging them. Majors are supposed to be hard!
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Dustin Johnson mullers his drive on the 500-yard par-four seventh. It finishes on an upslope which is so dry that the ball starts wandering back towards the tee. It's not all bad for DJ - he's got no more than a 9-iron left.
Rory McIlroy fires pin-high on the sixth - he needs a birdie or two to ease his cut nerves.
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Another shot gone for Henrik Stenson at the 15th and he is two over after six, three under for the tournament. Dustin Johnson in for par on six to stay one one behind Patrick Reed who slides in from a yard on the fifth to stay six under.
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Mickelson wanders over to the first tee. It's playing as a par-five today remember. He's drilled a three-wood down the middle. He needs a solid back nine just to make sure he's here for the weekend, never mind trying to wrap up his career grand slam.
Woods with much to work on
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"I wanted to shoot five or six today," said Tiger Woods after he bowed out of the tournament today, finishing well off the pace on +16.
"I wanted to be on the other side of it. I hit a little bit better today, but again, I made nothing.
I didn't make any putts the first two days.
"I just continue practicing, continue working on it. And hopefully it will be a little bit better."
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Andy, Armagh: Dustin Johnson's length off the tee gives him a huge advantage this week at this very long Chambers Bay course. However, the problem with him is that he always has a potential double or triple bogey in him on each round.
To win a major championship at this level with this sort of company on the leaderboard he can't afford to let that happen. Four solid rounds are needed, but Dustin Johnson rarely delivers that.
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Dustin Johnson out of the rough on the sixth and straight into sand.
Colin Montgomerie is hunched over his par putt on the 14th but he's back to level after a second successive bogey.
We've not seen much of Bubba Watson - chiefly because he's had three bogeys and dropped out to +3. But here he is on the 18th, his ninth, rolling in a birdie. He is playing with Phil Mickelson who has had a troubling nine holes. Another shot slips away on the 18th and he is back to +2.
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Henrik Stenson is on the par-three 15th, the downhill hole towards the sea and that would have looked great in the air. Straight at the flag. But it is fractionally short and starts rolling back towards the sand. It stays out of the bunker but rather than having a 10-footer for birdie, it's more like 40.
Reed in the (outright) lead
Patrick Reed takes the lead out to six under. The American has had a blistering start with two birdies in his opening four holes.
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From the slate grey sand, Rory splashes out with a pitch and run shot that wanders towards the hole and comes to rest a couple of inches to the right. Terrific effort.
Here's Monty on the 14th, up and across the green - I say green, it's more of a sandy brown - and that is rolling eight feet past.
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Justin Rose was in the same playing group as Jason Day, who collapsed on his way to the ninth green in an apparent recurrence of vertigo that he has suffered before.
"He seemed chirpy, buoyant all day. That was out of the blue, for sure," said Rose.
"It was a pretty severe bit of hill that he was sitting on. I thought maybe twisted his ankle."
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Rory McIlroy is in the same bunker Dustin Johnson has just left on the par-four fifth. The world number one needs another sand save otherwise he's right on the cut mark, which is currently +3.
A rare mistake from Henrik Stenson on the 14th. His 12-foot par putt pulls up short and he is dropping back to four under.
Day update
Australia's Jason Day had a bit of a turn as he was finishing up his round a little earlier. He collapsed on the ninth before receiving medical attention and then getting up to finish his hole and round.
His agent Bud Martin said in a statement: "Jason is being treated on site at Chambers Bay after feeling dizzy near the end of his round. We will provide more information later today after getting through the medical evaluation process. Jason wants to express his appreciation for all the good wishes from so many fans and friends."
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Mickelson's 30-foot birdie putt pulls up a couple of inches short, while Dustin Johnson flicks out of the sand on five and has an anxious wait to see if his ball has gone far enough to hold on the green. It does and he's quickly up marking it. He then knocks in the 10-foot par putt.
Back on the fourth, Rory McIlory is up and down from the sand for a par to stay two over but Colin Montgomerie leaves his par-putt short on the 13th to go back to one under.
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Straight on to the 17th and Mickelson comes within a whisker of smashing into the pin with his tee shot. I doubt the ball would have dropped had it hit the stick but it gave the crowd reason to "ooh" and "aah".
Henrik Stenson has been in a bit of trouble on the par-four 14th. How do I know? He's facing a wedge to the green for his third shot. He fires straight at the flag and his ball lands and stops 10 feet short.
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Phil Mickelson in for par on 16 after wonderfully creative second shot to the par-four green that landed well short and utilised the humps and bumps to give him a birdie look.
Dustin Johnson comes up a fraction short with his approach on the fifth and that spells trouble. His ball thinks about stopping 20 feet short of the pin but then decides it fancies a wee meander in to the solitary bunker protecting the green. A tough break.
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John McEnerney: Stenson has got that late 2013 form back again & if that putter stays hot it'll be easier to assemble a Liatorp than 2 catch him
A Liatorp is a particular furniture range at a well-known Swedish flat-pack purveyor in case you were wondering...
Ah, here is John with more information:
John McEnerney: "The Liatorp is called the "divorcemaker" by its makers - the most difficult item to assemble"
Critical Casey
England's Paul Casey had a one-under 69 today and he is +1 for the tournament.
He told BBC Radio 5 live: "Anytime you break par at the U.S. Open is not bad."
However Casey has been the latest player to criticise the state of the greens at Chambers Bay. "Maybe they are trying to recreate when they played US Opens a hundred years ago!" he said.
"They are not good. It's a very blotchy surface, a very difficult surface to putt on. They are not enjoyable, but it is the same for everybody, so I am trying to embrace it as much as I can. It is what is it. Do we wish we had better playing surfaces? Of course we do."
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Solid start for Sergio Garcia, three pars after a birdie at one and he is one under. Four holes and four pars for Henrik Stenson and that kind of steady play might just be enough to see him retain his share of the lead come the end of play.
Dustin Johnson is back alongside Stenson after knocking a birdie in at the fourth.
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That means Monty is the best Brit at Chambers Bay. His fellow Scot Marc Warren, who had a two-under 68 on day one, has had a shocker of an opening. A bogey, double bogey start has seen the 34-year-old drop to one over.
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Dave: Monty will finish top 6 and remind us how good he is
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It's birdie time for Colin Montgomerie though and suddenly the Scot is up to two under and just three off the lead. He couldn't, could he?
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An expert up-and-down by Phil Mickelson keeps him level par. But Rory McIlroy is dropping back to two over after missing his par putt on three. It could be worse. He could be Matt Kuchar. The American has just tripled the par-four fourth and he is one over.
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So who's staying up late with his this Friday night? If you think you can use the excuse of having to be up in the morning to take the kids to football, cricket, swimming, horse riding etc...then think again. I'm doing the football run and I'm staying right here.
Who will be our halfway leader and what will that score be? Will Phil and Rory slide away?
Text us your US Open thoughts on 81111 or Tweet #bbcgolf
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Patrick Reed thinks a lot of himself. In March 2014, after winning only his third Tour event, he pronounced himself as one of the world's top-five players.
Bold. But maybe correct.
He is up to 15 in the world in the latest rankings, rising fast and he has been remarkably consistent tee to green so far at Chambers Bay.
He has found 18 of 20 green in regulation so far - 90% success rate and clear of the field.
Reed in the lead
Cole Hammer, the 15-year-old who was born this century - I know - launches his drive down the first. He is starting on +7 and needs a minor miracle to extend his stay. I'm not sure he'll be too fussed if he doesn't.
Up on the second Patrick Reed knocks in for birdie and he joins Henrik Stenson and Jordan Spieth at -5.
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Henrik Stenson bisects the 13th fairway - it's the widest on the course at 105 yards. Rory McIlroy is wayward with his tee shot on the par-three third but he is at least on the green - it's 50 feet plus for birdie and his attempt does not threaten the hole. A tough eight-footer for par coming up.
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Colin Montgomerie showing terrific course management on the short par-four 12th. Rather than taking on the 284-yard hole, he lays up shot and fires a wedge to five feet.
Phil Mickelson is up on the elevated 15th tee looking down towards the green 144 yards away and the Puget Sound water behind it, glistening in the sunlight. It's all rather pleasant. Except Mickelson's ball plugs in the bunker protecting the front edge.
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The last men out of the hutch are away. Among them is Rich Berberian Jr. The American was 156th and last after round one following a 13-over 83. Northern Ireland's Darren Clarke, who is currently last, will be watching his progress with interest one would imagine.
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Rory McIlroy's birdie attempt on two stays up but par will do. Phil Mickelson knocks in his five-footer but that's two dropped shots in his first five holes and he is back to one over.
Dustin Johnson knocks in his bogey putt on three and we have just two joint leaders. Jordan Spieth is safely in the clubhouse on five under. Henrik Stenson has 15 holes to play.
Mickelson magic
Dustin Johnson will be dropping at least one. His first shot out of the bunker ends up back in the sand. His third finds the green but he's got half a dozen feet to just go four under.
Back on 14 and Phil Mickelson plays the kind of shot only Phil Mickelson can play. He is only five yards from the flag but his ball balloons about 20 feet in the air before coming to rest short of the hole. He then stumbles back into the bunker. Bogey putt coming up.
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Dustin Johnson about a yard from perfect with his tee shot on the third. But rather than kicking down left off the bank, his ball trickles back towards a bunker, gathering pace with each revolution before it comes to rest in the sand.
Phil Mickelson playing scratchy golf on 14, his approach to the green gets caught up between the rough and sand aside the green.
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Phil Mickelson in a spot of bother on 14, in a fairway bunker and he can only wedge out.
The projected cut mark has been brought in to +3. That puts the likes of defending champion Martin Kaymer in trouble. He bogeyed his opening hole and is +3.
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BBC Scotland's Tom English: Tiger Woods: It's like watching Shakespeare struggling to write a note to the milkman. Uncomfortable viewing.
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Dustin Johnson's birdie putt doesn't have the legs so he stays at five under. Phil Mickelson misses another birdie chance on 13.
On the 11th and more magic from Monty who fires right from the fairway and uses the contours to bring his ball to within 15 feet.
Over on three and Graeme McDowell, who is five over par, has a tap-in birdie after his tee shot on the par-three hole scoots round the back of the green, flirts with the bunker and ends up inches from the cup. A staggering shot.
Birdie for Rory
Rory from below the green on one and that's a decent chip to around 15 feet. Birdie chance coming up. And he drains it. An early move by the world number one who gets to one over. Up on the second, Dustin Johnson finds the heart of the green in regulation.
Over on 11 Henrik Stenson knocks in a short par putt to stay five under.
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James Richards: My money is on Stenson for clubhouse leader after round two
Bubba frustrated
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On the 13th Bubba Watson, looking like a tub of raspberry ripple ice cream, fires at the flag. It must have looked good from where he was - the ball slipped no more than a couple of inches past the hole but it just would not stop and rolled to the back of the green, 30 feet by.
"Wow," mutters Bubba as he strides after it. "I must be the only man to hit eight iron into this green (the 13th is a 550-yard par four) and even I can't get it to stop."
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Maybe the bookies know something. Monty tugs his birdie putt before hurriedly knocking in for par. A big opportunity missed.
On the first, Rory McIlroy is out with a three-wood and hacking out of the rough and his ball shoots forward and trundles down to the left of the green. Dustin Johnson just made par from down there and I think Rory would settle for that too.
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Phil Mickelson misses his birdie putt on 12 but is safely in for par to stay level. Henrik Stenson also in for par on the 10th to stay five under.
Colin Montgomerie was 500-1 at the start of play yesterday. How good do those odds look at this very moment? The Scot has just nailed a hybrid on the 10th to six feet. An opening birdie?
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Back on the tee and defending champion Martin Kaymer of Germany finds the fairway. He is starting at two over. That's the same as playing partner Rory McIlroy who goes down the left edge and his ball snags in the cabbage. He may struggle to get up in two from there.
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On the first, Sergio Garcia asks his ball to go right and it obliges, staying away from the nasty slope that has taken many a ball way down left of the green. He has a monster putt of what must be approaching 100 feet. Adam Scott goes further right and is rewarded as the ball bounds down off the hill to 40 feet shy.
Dustin Johnson is also imploring his ball to stay right. It doesn't and skips down were many before have gone.
Monty finds the fairway
The completely unique swing of 2003 US Open champion Jim Furyk sends his ball careering down the 10th fairway. He is followed by Miguel Angel Jimenez and Colin Montgomerie. The 51-year-old Scot rolled back the years on Thursday to card a one-under 69. Another one of those today will do very nicely thank you. He is safely down the middle.
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Brandt Snedeker, playing with Stenson, comes in from the right of the green and his ball curls to a stop eight feet the other side of the hole.
Over on the first, which is playing as a par five today, Matt Kuchar flips a wedge onto the green and he's got a 20-footer for birdie. He misses it but has a straightforward one to stay three under.
On the 12th, Mickelson comes up 20 feet short with a putt from the off the front of the green.
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Over on the 10th the other co-leader, Sweden's Henrik Stenson, is also away with a drive to the fairway and his second on the par four skips 10 yards past the hole and up a little slope which returns the ball to within 10 feet of the flag. Big birdie chance first up.
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Joint leader Dustin Johnson gets his second round under way and he's a little fortunate not to find a fairway bunker. Playing partners Adam Scott and Sergio Garcia are also cleanly away.
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Back on the 11th and both Mickelson and Bubba leave their birdie attempts on the green. Tap-in pars and off to the 12th tee we go.
Spieth's spiel
Here's our joint leader Jordan Spieth on his round: "Two under each day is a goal that I want to do. My putter was on today, my driver wasn't but when your putter is on you can salvage a round. This is golf's toughest mental test. It's about testing patience. If my putter continues to stay hot we'll be in good shape."
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At least Tiger will not be last. At the moment, that dubious honour belongs to 2011 Open champion Darren Clarke. The Northern Irishman had a 10-over-par 80 on Friday to finish +17.
Tiger Woods misses cut
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We skip back to the ninth to see the end of Tiger's round and it's an untidy finish. A snaking 40-footer slides four feet by and the par putt lips out. It's another bogey for the world number 195 and he ends with a six-over 76 and +16 for the tournament. And that folks, is the end of his involvement in this tournament.
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Back on the ninth, Justin Rose two-putts for par and the Englishman is signing for a level-par 70 - that triple bogey seven on the seventh being his downfall. Still at two over for the tournament, he's far from out of this.
Back on the second and Phil Mickelson finds the green with his second shot but he's got a 30-footer for birdie. Playing partner Bubba Watson follows Phil's line out right of the flag and his ball picks up more pace off the hill and he's left with a more makeable dozen feet for birdie.
Latest scores
-5 Spieth (US) F, D Johnson (US) Stenson (Swe) -4 Grace (SA) F, Martin (US) 17, Reed (US). -3: Luiten (Ned) F, Finau (US) F, Summerhays (US) F, Kuchar (US)
Selected others +1 P Casey (Eng) F: +2 Westwood (Eng) F; Rose (Eng) F; +4 Donald (Eng) F +5 Poulter (Eng) 17 +15 Woods (US) 17
Peter Scrivener here to take you through the next couple of hours.
And I start on the 10th hole with Phil Mickelson immediately dropping back to level par. A poor second shot that missed the green proves costly, although Lefty's short par putt looked makeable. He's got 17 holes left to make inroads into the lead.
Spieth into lead at -5
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Jordan Spieth's putting today deserves a slice of lead pie and that is exactly what he is getting.
He drains from eight to 10 feet on the final green of his round. That takes him to five under and back to the top of the leaderboard, alongside Henrik Stenson and Dustin Johnson who are yet to start their day's work.
Day done on -2
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Jason Day is wobbling like he has taken a uppercut on the chin. Or sunk 12 Saturday-night pints.
I'm not surprised the Australians' vertigo was triggered as he made his way down from the crow's nest of tee down to the ninth green far below. It is really steep.
He regains his footing to splash out of the sand to within ten feet. Par putt next. A little shakily, it slips by. Four feet for bogey. In she goes and he is done at two under.
Westwood done on +2
Lee Westwood has signed off on his round in very ugly style.
A triple bogey seven on the 18th leaves him the wrong side of par on two over.
Shame. A damn shame.
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Day's collapse came right in front of the grandstand on the ninth. Jordan Spieth shows some nice empathy, telling some rubber-necking spectators to put away their camera phones.
Spieth has hit a nice approach by the way and has a birdie chance.
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We have a problem out on the ninth.
Jason Day is in a crumpled heap on the fairway. It looks like he has collapsed rather than fallen. He suffers from vertigo and that is being pinned as the likely cause.
Medical attention has reached him already and he is sitting up and talking with the doctors.
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Two things to mention as Phil Mickelson, Bubba Watson and Angel Cabrera tee off together.
First, someone shouts "get in the hole" on a par-five opener like a trained gibbon.
Second, the announcer practically gives Mickelson and Watson's zip codes, namechecking their home town and state. Cabrera is just "from Argentina". A chance to impart a much-needed geography lesson missed.
Grace finishes -4
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Branden Grace has a real ogre of putt to contend with on the last. This is for par. It draws round, but not enough.
He makes the four-footer coming back to clock off with a three-under round for the day, four-under overall.
Our leaderboard is almost back to as you were. Overnight top dogs Dustin Johnson and Henrik Stenson have just Ben Martin for company.
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Jordan Spieth with the touch of a butterfly-collecting brain surgeon as he scoops a lovely little chip up to within five feet on eight for a birdie chance.
Nope. The ball slips by.
Poulter back to +5
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The halfway snip of the field is going to take out Ian Poulter as it stands.
The Englishman dropped two shots on six and is five over. He has three holes to smoke out the birdie that will extend his stay at Chambers Bay.
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Ben Martin has been consistency personified today. A bogey six at the first, but since then it has been all pars with three birdies thrown in.
That has been been rewarded with a share of the lead. He has never made it beyond the first two rounds before.
He is going to today. The cut is projected to fall at five over by the way.
Latest scores
-5 Grace (SA) 17, Martin (US) 15, D Johnson (US) Stenson (Swe) -4 Spieth (US) 16, Reed (US). -3: Luiten (Ned) F, Finau (US) F, Summerhays (US) 17, Kuchar (US)
Selected others: -1 Westwood (Eng) 17; +3 Rose (Eng) 16;+1 P Casey (Eng) 17; +4 Donald (Eng) F +14 Woods (US) 16
Spieth & Summerhays drop back. Grace into joint lead
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Jordan Spieth cannot dust up the scrapes on the seventh. His round is dented by a bogey, three-putting after perching himself in a nightmare position over the hole with his initial approach.
Spieth's place among the front runners is taken by South African Branden Grace with a birdie on the par-three 17th.
And Daniel Sumerhays hits trouble. A double-bogey six on seven has him back to three under.
Rose to +3
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Justin Rose's round has just gone into reverse.
That tricksy little minx of a seventh is to blame again.
The Englishman picks up a triple bogey seven and is back to three over.
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Jordon Spieth on the par-four seventh has a pretty much unputtable birdie chance. He is knocking along a precipice, down a steep slope. It runs about 12 feet by and he will be pretty happy with that...
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Freight and passenger trains still chug through Chambers Bay with the tracks running right alongside the 16th and 17th fairways.
If Justin Rose landed his drive on a passing express train, he could have had a tricky second shot from Canada.
The Englishman didn't. He is level par overall with three holes to play.
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Rory McIlory touches the peak of his dazzling white cap as he is cheered out to practice by some of the patrons. Actually his outfit is pretty much all white - he looks like he is fresh out of a washing powder advert.
The Northern Irish young gun - two over - gets going at 22:28 BST.
Westwood to -1
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Lee Westwood has struck birdie juice.
The man from Worksop has sunk a long snaker of a birdie putt on the par -three 15th. That is his sixth in nine holes.
He is four under for the day, one under overall.
Latest scores
-5 Summerhays (US) 15, Spieth (US) 15, D. Johnson (US), Stenson (Swe) -4 Grace (SA) 15, Martin (US) 13, Reed (US). -3: Luiten (Ned) 17, Kuchar (US)
Selected others: -1 Westwood (Eng) 15;E Rose (Eng) 15;+2 P Casey (Eng) 15; +4 Donald (Eng) +13 Woods (US) 14
Holmes back home on two under
J.B Holmes on the last with a piddly little putt for a birdie and three under.
Snatched at it! It whips clean by and instead he has an awkward four footer back for par. A long, hard look at it...In he comes...and down it goes.
A very impressive four under for the day for the American.
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Joint leader Daniel Summerhays tells his caddy he would be happy to land in the front of the greenside bunker as he stands over his second in the wild stuff on the par-four seven.
Seemed pessimistic, but that proves about right.
He undercooks and rolls back 40 yards. Them's the breaks on Chambers Bay. Plenty to do from there for par.
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Dutchman Joost Luiten is getting his feet under the table.
Successive birdies on 15 and 16 shift him onto one under for the day and three under overall.
Alongside him in a share of eighth is Matt Kuchar.
Oh I say! A moment of magic off the face of Ian Poulter's sandwedge as he chips in from the sand for a birdie on four. Three over for the Postman.
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Jordan Spieth's putter is red hot and its owner is ice cool.
His par putt on five - a tricky eight-footer made all the more difficult by the roller-coaster greens - disappears down the chute.
He keeps his share of the lead.
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Lee Westwood is posting some nice numbers.
Birdies on seven and eight are followed by more on 10 and 12. Two under for the day and one over overall.
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Jordon Spieth plays golf better than he swears.
The American plunges his second shot into a greenside bunker on the par-four five and responds with "Dang it Jordan!".
Still five under and with a share of the lead though. And that is a decent recovery shot from the sand. He has a chance of keeping up top of the leaderboard.
Tiger Woods has had a wobble with bogies on two and three taking him to three over for the day and 13 over overall.
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A less kind man than me might suggest that Miguel Angel Jimenez looks increasingly like he is starring in a Spanish remake of Gregor Fisher's 90s sitcom "Baldy Man".
And he is still the coolest man in golf by a country mile.
He has arrived on the course and will begin his round at 22:28 BST.
Phil Mickelson is also in the house. He will be hunting the one Major not on his mantelpiece from 21:33 BST.
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We have the first punt on how many Majors Jordan Spieth will be able to tell the grandkids about winning once he has hung up his spikes.
TheSultan: "Spieth gets fewer than McIlroy. McIlroy 10, Spieth 7 or 8."
Your guess is welcome on #bbcgolf and 81111 on text.
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Jason Day gets digging in a bunker at four.
The Aussie's ball looks like a comet crashed in the moon, leaving him a shot out of a dirty great crater in the grey surface of the sand.
He escapes with a bogey five, which is not too shabby. He is back to two under.
Grace back to -4
Daniel Summerhays with a chance to take an exclusive hold of the lead with a birdie putt at five? But it slides and he stays at five under.
Branden Grace has dropped straight out the backdoor, missing his par putt at 13 to slip back to four under.
Grace into a share of the lead
Branden Grace? Come on down!
The South African makes it a party of five at the top of the leaderboard with a birdie three at 12.
Jordan Spieth, Daniel Summerhays, Dustin Johnson and Henrik Stenson are already sipping the rare atmosphere in the big-chance saloon.
Clarke suffering
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Darren Clarke is rock-bottom last, propping up all 155 others in the field. His scoreboard is a horror show - starting with a triple-bogey seven and featuring another seven dropped shots.
Two birdies have repaired some of the damage, but not much. He is 15 over for the tournament, eight over for the day.
Overnight joint-leader Henrik Stenson strolls into Chambers Bay looking as cool as a cucumber, even with a television camera poking in his face.
The Swede smoothes down his eyebrows Fonz-style with a wipe of a wetted finger and points down the lens. Nice.
Summerhays into a share of the lead
And then there were four...
American Daniel Summerhays acknowledges the cheers from the crowd as he sinks a birdie putt on four to move into a share of the lead alongside Jordan Spieth and clubhouse-bound pair Henrik Stenson and Dustin Johnson.
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Australian Jason Day - a man with skills to win a major, but perhaps not the mentality - is showing up nicely.
After picking up birdies on one and two, he holes a knee-knocking five-footer on three for his par.
He is one under for the day - three under overall.
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If you want to get in touch with this live text, we are just a text, tweet or social media musing away.
To start, anybody fancy a quick guess on what spread you would get for Jordan Spieth career Majors?
North of five, south of ten? What do you reckon?
Cloudless in Seattle
It is a sparkling day in Seattle by the way. Fine sunshine and a breath of wind, but not too significant.
Nothing to complain about meteorologically for the players.
American Daniel Summerhays - playing in only his second US Open - has moved into a share of second by the way.
Two birdies in his last three holes to move to four under. Six left in his round.
Out of the Woods?
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Ah, yes Tiger, Tiger.
Not so much "burning bright" as "playing somewhat less than alright" yesterday.
He scored a 10-over 80 yesterday - the lowlight of which was a triple-bogey seven on 14.
He has steadied the ship so far today - plugging away at one over for the day after 10 holes.
Latest scores
So this is where we stand, as we stand.
-5: Spieth (US), D. Johnson (US), Stenson (Swe) -4: Grace (RSA), Martin (US), Reed. -3: Lovemark, Summerhays, Kuchar (all US)
Selected others:-1 Rose (Eng) +1 Westwood (Eng) +4 Donald (Eng) +12 Woods (US)
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Hang on! Birdie four at the first and Jordan Spieth is back at the top of the leaderboard again, sharing the spotlight with overnight leaders Henrik Stenson and Dustin Johnson who are yet to start their second rounds.
Full scoreboard coming right up...
Master of the course
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One man who didn't hang around to dish the dirt on the course is Jordan Spieth.
The Masters champion just gets on with scoring low as a limbo dancer's shoulder blades.
He is the headline-maker so far in the second round of the US Open.
He started like a train, scoring four under for his first eight holes to take the lead on six under.
He has slipped back with a double-bogey six on 18, but is the main mover and shaker so far.
Live Reporting
Mike Henson and Peter Scrivener
All times stated are UK
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Latest PostPost update
An eventful day for Monty who went from the best-placed Briton to looking like he was set for an early return ticket home.
A bogey on the last has sent him to five over. The cut was projected at four over. But with the top 60 and ties making the weekend five over will make it.
So he will ride again tomorrow, and so will we.
We go again to bring you all the news from Chambers Bay, this time with added BBC Radio 5 live commentary.
See you there.
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Henrik Stenson signs off on an underwhelming four-over round to finish only one under overall.
Meanwhile Colin Mongomerie is backed right up to the wall. The Scot is four over. Those on five over look set to miss out.
He is on that crazily-steep par three ninth.
Latest scores
-5 Spieth (US) F, Reed (US) F, -4 Grace (SA) F, D Johnson (US) F -3: Luiten (Ned) F, Finau (US) F, Summerhays (US) F, Martin (US) F
Selected others +1 P Casey (Eng) F: +2 Westwood (Eng) F; Rose (Eng) F; +3: Mickelson (US) F +4 Donald (Eng) F,McIlroy (NI) F, Montgomerie (Sco) 17, +5 Poulter (Eng) F +16 Woods (US) F
Projected cut: +5
For a full leaderboard, click this way.
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The ball pauses on the edge, looked down the manhole and decided it didn't want to get subterranean.
Patrick Reed had to put up with a bogey on the last - but he still has a share of the lead to look at.
Jordan Speight and Dustin Johnson are also at the top of the pops.
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Patrick Reed headed to the seaside on the last. No time for that, there is a halfway stage lead to wrap up.
Up and out to the green a very faint chance of a birdie. Deep consultation with the caddy, but what does he know? The ball dribbles into no man's land. Still work to do.
McIlroy slips to +4
Rory McIlroy's teasing round - hinting at a revival, posturing for a charge - has crashed and burned with three dropped shots in the final two holes.
After the double bogey on 17, comes a bogey on 18, leaving him high, dry and handsome on four over.
He is just one shot the right side of the cut-off line as it stands.
Johnson back to -3
Dustin Johnson's creaky final few holes culminates in a bogey on 18. He left a fair few shots out that and could be clear of the rest.
As it is, three bogies in the last four holes leave him four under par and one over for today. He is two shots off Patrick Reed and one behind Jordan Spieth on the leaderboard.
McIlroy slips to +3
Never mind the wheels, the wingmirrors, axel and engine have dropped out off Rory McIlroy's round on 17.
The Northern Irishman had chiselled and clawed his way back to a decent score over a matter of hours, and has now chucked it in the bin in minutes.
A three-putt back from that heavy-handed second shot means he cards a double-bogey five on 17.
He is a distant three over overall.
Day update
A further update on Jason Day, who collapsed on the ninth hole earlier today,from his agent Bud Martin: "Jason was diagnosed to have suffered from Benign Positional Vertigo. He was treated locally by Dr. Robert Stoecker and Dr. Charles Souliere and is resting comfortably.
"His condition is being monitored closely and he is hopeful he will be able to compete this weekend in the final rounds of the US Open. He wants to thank all who treated him at the Franciscan Medical Group and thank all of the fans and friends who have reached out to he and his family."
Reed moves into sole lead at -6
Patrick Reed is still dead-eyed and zoomed in on the prize though.
The American taps in his birdie putt on 16 and marches off to the two final holes with a seven-under lead to lord over everyone else in the field.
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Rory McIlroy's hands are heavy as lead on 17, clumping the ball almost through the back of the green.
He has given himself loads to do here. A good 15 yards to make up on the return trip.
Concentration is fraying among these last starters.
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At the top of the leaderboard, it is Patrick Reed who is the coming force.
He feathers a delicious second shot up to within four feet on 16 just as Dustin Johnson yanks his drive right on the last.
Exclusive hold of the lead is surely in the post already.
Latest scores
-5 Spieth (US) F, Reed (US) 15, D Johnson (US) 17-4 Grace (SA) F. -3: Luiten (Ned) F, Finau (US) F, Summerhays (US) F, Martin (US) F
Selected others +1 P Casey (Eng) F: McIlroy (NI) 16 +2 Westwood (Eng) F; Rose (Eng) F; +3: Montgomerie (Sco) 15, Mickelson (US) F +4 Donald (Eng) F, +5 Poulter (Eng) F +16 Woods (US) F
Projected cut: +5
For a full leaderboard, click this way.
Johnson & Reed back to +5
Within moments of each other, the joint leaders Dustin Johnson and Patrick Reed both slip back into the clutches of the clubhouse leader Jordan Spieth.
Their dropped shots on 17 and 15 respectively means it is a three way carve-up at the top of the leaderboard.
McIlroy stays on +1
Rory McIlroy zinged his drive on the par-four 16, but he misses with his birdie putt and stays in positive figures.
Meanwhile a train clatters through on the tracks adjacent to the green.
Not Hammer's time
Fifteen-year-old Cole Hammer is in the last group out on the course.
The third-youngest player ever to compete at the US Open, and so far it has been a learning experience at best for the Houston-based amateur.
He is nine over for today after a triple -bogey seven on 11.
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Putt wobbling all over a sun-baked rough-cut green?
Having to change into your spikes in a tent because the clubhouse is too small?
Well, world's best golfers take a look at the view and a deep breath. This is not a bad office from which to do a well paid job.
Mickelson move up to +3
Phil Mickelson is scrapping for his life. He emerges from the eighth green - his penultimate hole - with a birdie two.
That shunts him up to three over and puts him the right side of the projected cut. The dream lives. For now.
Reed backs to -6
This field has its own centre of gravity, sucking the leaders back towards the rest and preventing them from getting clear.
Patrick Reed also ships a stroke on the tricky 12th. He is into a share of the lead with Dustin Johnson.
Reed leads on -7
Yep, that is right. Patrick Reed is alone in the cockpit after Dustin Johnson prods a putt right of the hole on the right on 15.
That one never looked like renewing acquaintances with the cup.
Latest scores
-7: Reed (US) 12 -6: D Johnson (US) 13, -5 Spieth (US) F -4 Grace (SA) F. -3: Luiten (Ned) F, Finau (US) F, Summerhays (US) F, Martin (US) F
Selected others +1 P Casey (Eng) F: +2 Westwood (Eng) F; Rose (Eng) F; McIlroy (NI) 13 +3: Montgomerie (Sco) 12+4 Donald (Eng) F, Mickelson (US) 16 +5 Poulter (Eng) F +16 Woods (US) F
Projected cut: +5
For a full leaderboard, click this way.
McIlroy saves par on 13
Rory McIlroy with a par that feels like a birdie or better.
He looked like he was on the hook on 13 after a horrible drive put him in the rough. But a fine recovery up and down - the second half a nerveless putt downhill - means the eagle he picked up on the previous hole is unscathed.
Mickelson to +4 and outside cut
Phil Mickelson's wait for a first US Open title will stretch out for to at least a 26th year as it stands.
The six-time runner-up has chalked up a second straight bogey - dropping a shot at seven - to slip to four over and outside the projected cut.
He has two more holes to haul himself, coughing and spluttering into the weekend.
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Rory McIlroy is in a world of pain on 13.
A punt out of the rough followed by an undercooked third leave him with an a very difficult up-and-down from below the level of the green just to make bogey...
Reed to -7 and share of lead
Say what you want about him, and plenty do, but Patrick Reed is brimful of fighting spirit and self-belief.
He knocks in an eagle putt on 12 and is back into a share of the lead.
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"Pick up another shot over his final six holes and Rory McIlroy will be at level par at the halfway stage. A great platform for a challenge with 36 holes to play and a fair wind behind him. He could, he just might, be involved in the Sunday shakedown."
Woah, hold your horses. There are a lot of ifs and buts in there and that is even before McIlroy fades his drive off the 13th tee, wide of the 105-yard landing strip and into the rough.
Reed back to -5, McIlroy to +1
Did the leaderboard move for you? It did for me.
Patrick Reed is straight back on the horse, teasing in a birdie putt on the 10th to return to -5 and a share of second.
Meanwhile Rory McIlroy finally sinks a putt for an eagle two on the 12th. That is him moving on up to +1.
Fun and games
Want to get an idea of the big-dipper greens at Chambers Bay?
This video, on Ian Poulter's Facebook page, is for you. The Englishman turns a one-foot putt into a three-footer via a 450-foot detour up and down a huge slope behind the hole
Reed back to -4
Patrick Reed had sole ownership of the lead an hour or so ago, but has come off the boil since. His third bogey in four holes takes him out to four under and only, only, a share of third.
Mickelson slips to +3
Phil Mickelson very nearly saves his skin with a marathon putt on the sixth, but it runs around the rim and stays out.
He is rapidly heading the wrong way.
Projected cut now at +4
The projected cut has gone out from three over to four over.
That means a reprieve for England's Luke Donald and Spanish sea dog Miguel Angel Jimenez as well.
Post update
Jordan Spieth is aiming to become only the sixth person in history to land both the Masters and the US Open crown in the same year.
The other five are none too shabby either: Craig Wood in 1941, Ben Hogan 1953, Arnold Palmer 1960, Jack Nicklaus 1972 and Tiger Woods in 2002.
Johnson to -7 and two-shot lead
Dustin Johnson slides his birdie putt right down the gullet of the 11th hole.
His advantage over the field and nearest challengers Patrick Reed and Jordan Spieth is up to two shots.
A red, white and blue look to the leaderboard and it is nothing to do with the Union Jack.
Eight of the top 12 are American.
Mickelson stays at +2
Ol' Lefty Phil Mickelson would surely be the most popular winner with the local punters up in the Pacific North West.
The American five-time Major winner has a birdie putt at the par-four fifth. But again it undercooked. He stays two over with four holes left on his card.
Reed back to -5
Patrick Reed drops back with a bogey on the ninth, to leave Dustin Johnson alone at the top of the leaderboard.
Rory McIlory goes limp-wristed over an uphill birdie putt on the 10th green. "Not up, not in." And that is neither. The whole field have been struggling with that putt. Give it some welly lads.
Stenson back to -4
Henrik Stenson marks his arrival on the front nine (he started on hole 10) with a birdie four.
The Swede is back to four under and a share of fourth place with South Africa Branden Grace
Better.
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Apparently Sergio Garcia is copping a bit of heat from some of the spectators after his less-than-complimentary comments about the greens yesterday.
He said they were "as bad as they look" after the first round. And they do look like your local municipal links after the greenkeeper mixed-up the weedkiller wrong.
"If my problem is saying what everyone thinks but they don't have the guts to say it, then I'm guilty of that for sure," added Garcia yesterday.
The Spaniard is two over for the round, putting him two over overall.
Reed into share of lead at -6
Patrick Reed comes off the eighth green - like some sort of Escher drawing, all deceptive slopes and red herrings - with a birdie.
Dustin Johnson has a chance to immediately re-establish his lead on the ninth, but his own birdie putt lacks legs.
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Nothing like the spontaneous expression of joy and fraternal love that is a high-five is there?
McIlroy still on +3
Rory McIlroy has a 10-foot birdie putt after safely making it down onto the dancefloor from the elevated tee on the par-three ninth.
Nothing is dropping for him today though. The ball stays north and his score stays on the high side as well.
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Patrick Reed has practically got a theodolite and set square out to measure up a mammoth eagle putt on the par five. Drain this and he is leading solo.
It is a risky one though, heading downhill. He gives it a tickle and even that was a bit heavy. He has six feet to negotiate back up the hill.
Johnson back to -6
Dustin Johnson's momentum is checked with a bogey four on the ninth.
He is still at the top of the tree though on six under. His lead over Ryder Cup compadres Jordan Spieth and Patrick Reed is down to one shot though as rounds the turn.
He is solid and secure off the 10th tee
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By the way, Dustin Johnson has the whole clan over to watch this charge at the top of the leaderboard.
Wife Paulina Gretzky, son Tatum and father-in-law Wayne are all at Chambers Bay.
If Tatum doesn't live out the plot of Happy Gimore with Dustin Johnson as his dad and Wayne Gretzky's daughter as his mum, there is no hope..
McIlroy stays +3
Rory McIlroy with a long look at a long-range birdie putt on the par-five eighth.
He might as well have been trying to read Ancient Greek as that green. The ball stayed stubbornly out left, refusing to break as he thought it might.
A frustrating day continues.
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Cheers Peter.
Rory McIlroy's indifferent form at least takes him out of the thorny "best-placed Brit" issue.
That honour is currently held by Marc Warren of Scotland on one under through seven, with Paul Casey, one over and done for his day, his nearest competition.
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Dustin Johnson on the par-three ninth. And he's in the sand. One yard from perfection.
Back on the eighth and Rory McIlroy is chipping his third from short of the green. It hops and skips and comes to rest 15 feet from the pin. If ever he needed a birdie.
Perhaps Mike Henson can bring him more luck than I. Let's find out...
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That's three birdies in five holes for Dustin Johnson on some of the hardest holes on the course. Sergio Garcia, by contrast, has shipped three in the last four.
Scotland's Marc Warren is fighting hard. A birdie on the 15th has got him back to one under for the tournament.
Johnson leads on his own
Big swing at the top of the leaderboard.
Dustin Johnson gets all aggressive with his eagle putt on the eighth but trundles in for birdie from five feet to get to seven under.
Patrick Reed pays the ultimate penalty for missing the fairway on the seventh. His third from the back of the green gets diverted by on a huge slope and the par putt stays up. He drops back to five under, level with Jordan Spieth.
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Sergio Garcia's decent start is in danger of unravelling. A bogey on the seventh and he's just raced a birdie putt on the eighth six feet past and his putting woes continue. The Spaniard suddenly out to +2.
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Patrick Reed has no cut pressures at the moment but he is playing to the seventh green out of the claggy rough to the left of the fairway. He can't hold the green and has a tricky up and down for par.
Colin Montgomerie gives himself a chance of picking up a shot on the par-three 17th with a decent tee shot into the guts of the green.
McIlroy under pressure
Rory McIlroy is in danger of missing the cut. His birdie putt from the back of the seventh green leaves him a dozen feet for par. But he's not making that and the world number one is right on the cut line at +3.
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Bubba Watson eyes up the bunker shot on the second and flies it way up into the air. It lands softly but he's got work to do for par.
On the seventh, Martin Kaymer's defence could be ending today. He doesn't borrow enough on a lengthy birdie putt and misses the 15-foot par putt that follows. He's back to +4.
Dustin Johnson finds the par-five eighth green in two. A 25-footer for eagle.
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Bubba Watson with a wild swish from the rough on the second and he is heading into a greenside bunker. He is +3 and on the cut mark.
Rory McIlroy smashed his drive down the seventh into Dustin Johnson country but he cannot match the American's accuracy with a wedge in his hand. His ball skips over the mound that Dustin's rolled back down towards the hole. Instead of a three-foot putt, Rors is facing a 40-foot birdie attempt.
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Niall: Dreams of Monty and Speith being paired together in the final round. Thirty years/stone between them, neck and neck going down the home stretch.
Dustin back on top
Back to the seventh for Dustin Johnson's birdie attempt. I did him a disservice. His approach finished three feet from the pin. A much easier putt and Dustin duly obliges to join Patrick Reed as US Open leader on six under par.
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Patrick Reed crouches down behind his birdie putt on the sixth. It's similar to the one Rory McIlroy just missed, maybe a touch longer and he misses to the right, just like Rory.
Sergio Garcia, never the greatest putter in the world, is a touch short with a birdie putt on seven but he is level for the round and tournament and hanging in there.
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Lee Westwood on Twitter: Played great today. Shame about 18. I know I made triple but it's a stupid par 4 and a great par 5. Sun and wind on this golf course all day. Chambers Bay will be brutal this afternoon. Great viewing.
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Dustin Johnson takes full advantage of his monster drive on the seventh. His short iron stops abruptly and then dribbles back towards the hole leaving a six-foot birdie putt.
Phil Mickelson misses a birdie opportunity on the par-five first but is in for par to stay +2.
Henrik Stenson's putting radar is also slightly off but he stops the rot of successive bogeys with a par on the 16th to stay three under.
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Rory McIlroy's birdie putt on the sixth races a couple of feet past but he has more nerve than Monty and holes out. Back down the fairway, Patrick Reed hits his approach pin high but he's 30 feet left of the pin.
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Monty for birdie on 15 from 20 feet and that's meandering right, a testy couple of feet for par. And he's tugged that left. A three-putt bogey and a third successive bogey sees the Scot back to one over par.
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James Bamford: Well done @usopengolf taking the pros out of their comfort zone and challenging them. Majors are supposed to be hard!
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Dustin Johnson mullers his drive on the 500-yard par-four seventh. It finishes on an upslope which is so dry that the ball starts wandering back towards the tee. It's not all bad for DJ - he's got no more than a 9-iron left.
Rory McIlroy fires pin-high on the sixth - he needs a birdie or two to ease his cut nerves.
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Another shot gone for Henrik Stenson at the 15th and he is two over after six, three under for the tournament. Dustin Johnson in for par on six to stay one one behind Patrick Reed who slides in from a yard on the fifth to stay six under.
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Mickelson wanders over to the first tee. It's playing as a par-five today remember. He's drilled a three-wood down the middle. He needs a solid back nine just to make sure he's here for the weekend, never mind trying to wrap up his career grand slam.
Woods with much to work on
"I wanted to shoot five or six today," said Tiger Woods after he bowed out of the tournament today, finishing well off the pace on +16.
"I wanted to be on the other side of it. I hit a little bit better today, but again, I made nothing.
I didn't make any putts the first two days.
"I just continue practicing, continue working on it. And hopefully it will be a little bit better."
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Andy, Armagh: Dustin Johnson's length off the tee gives him a huge advantage this week at this very long Chambers Bay course. However, the problem with him is that he always has a potential double or triple bogey in him on each round.
To win a major championship at this level with this sort of company on the leaderboard he can't afford to let that happen. Four solid rounds are needed, but Dustin Johnson rarely delivers that.
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Dustin Johnson out of the rough on the sixth and straight into sand.
Colin Montgomerie is hunched over his par putt on the 14th but he's back to level after a second successive bogey.
We've not seen much of Bubba Watson - chiefly because he's had three bogeys and dropped out to +3. But here he is on the 18th, his ninth, rolling in a birdie. He is playing with Phil Mickelson who has had a troubling nine holes. Another shot slips away on the 18th and he is back to +2.
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Henrik Stenson is on the par-three 15th, the downhill hole towards the sea and that would have looked great in the air. Straight at the flag. But it is fractionally short and starts rolling back towards the sand. It stays out of the bunker but rather than having a 10-footer for birdie, it's more like 40.
Reed in the (outright) lead
Patrick Reed takes the lead out to six under. The American has had a blistering start with two birdies in his opening four holes.
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From the slate grey sand, Rory splashes out with a pitch and run shot that wanders towards the hole and comes to rest a couple of inches to the right. Terrific effort.
Here's Monty on the 14th, up and across the green - I say green, it's more of a sandy brown - and that is rolling eight feet past.
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Justin Rose was in the same playing group as Jason Day, who collapsed on his way to the ninth green in an apparent recurrence of vertigo that he has suffered before.
"He seemed chirpy, buoyant all day. That was out of the blue, for sure," said Rose.
"It was a pretty severe bit of hill that he was sitting on. I thought maybe twisted his ankle."
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Rory McIlroy is in the same bunker Dustin Johnson has just left on the par-four fifth. The world number one needs another sand save otherwise he's right on the cut mark, which is currently +3.
A rare mistake from Henrik Stenson on the 14th. His 12-foot par putt pulls up short and he is dropping back to four under.
Day update
Australia's Jason Day had a bit of a turn as he was finishing up his round a little earlier. He collapsed on the ninth before receiving medical attention and then getting up to finish his hole and round.
His agent Bud Martin said in a statement: "Jason is being treated on site at Chambers Bay after feeling dizzy near the end of his round. We will provide more information later today after getting through the medical evaluation process. Jason wants to express his appreciation for all the good wishes from so many fans and friends."
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Mickelson's 30-foot birdie putt pulls up a couple of inches short, while Dustin Johnson flicks out of the sand on five and has an anxious wait to see if his ball has gone far enough to hold on the green. It does and he's quickly up marking it. He then knocks in the 10-foot par putt.
Back on the fourth, Rory McIlory is up and down from the sand for a par to stay two over but Colin Montgomerie leaves his par-putt short on the 13th to go back to one under.
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Straight on to the 17th and Mickelson comes within a whisker of smashing into the pin with his tee shot. I doubt the ball would have dropped had it hit the stick but it gave the crowd reason to "ooh" and "aah".
Henrik Stenson has been in a bit of trouble on the par-four 14th. How do I know? He's facing a wedge to the green for his third shot. He fires straight at the flag and his ball lands and stops 10 feet short.
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Phil Mickelson in for par on 16 after wonderfully creative second shot to the par-four green that landed well short and utilised the humps and bumps to give him a birdie look.
Dustin Johnson comes up a fraction short with his approach on the fifth and that spells trouble. His ball thinks about stopping 20 feet short of the pin but then decides it fancies a wee meander in to the solitary bunker protecting the green. A tough break.
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John McEnerney: Stenson has got that late 2013 form back again & if that putter stays hot it'll be easier to assemble a Liatorp than 2 catch him
A Liatorp is a particular furniture range at a well-known Swedish flat-pack purveyor in case you were wondering...
Ah, here is John with more information:
John McEnerney: "The Liatorp is called the "divorcemaker" by its makers - the most difficult item to assemble"
Critical Casey
England's Paul Casey had a one-under 69 today and he is +1 for the tournament.
He told BBC Radio 5 live: "Anytime you break par at the U.S. Open is not bad."
However Casey has been the latest player to criticise the state of the greens at Chambers Bay. "Maybe they are trying to recreate when they played US Opens a hundred years ago!" he said.
"They are not good. It's a very blotchy surface, a very difficult surface to putt on. They are not enjoyable, but it is the same for everybody, so I am trying to embrace it as much as I can. It is what is it. Do we wish we had better playing surfaces? Of course we do."
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Solid start for Sergio Garcia, three pars after a birdie at one and he is one under. Four holes and four pars for Henrik Stenson and that kind of steady play might just be enough to see him retain his share of the lead come the end of play.
Dustin Johnson is back alongside Stenson after knocking a birdie in at the fourth.
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That means Monty is the best Brit at Chambers Bay. His fellow Scot Marc Warren, who had a two-under 68 on day one, has had a shocker of an opening. A bogey, double bogey start has seen the 34-year-old drop to one over.
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Dave: Monty will finish top 6 and remind us how good he is
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It's birdie time for Colin Montgomerie though and suddenly the Scot is up to two under and just three off the lead. He couldn't, could he?
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An expert up-and-down by Phil Mickelson keeps him level par. But Rory McIlroy is dropping back to two over after missing his par putt on three. It could be worse. He could be Matt Kuchar. The American has just tripled the par-four fourth and he is one over.
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So who's staying up late with his this Friday night? If you think you can use the excuse of having to be up in the morning to take the kids to football, cricket, swimming, horse riding etc...then think again. I'm doing the football run and I'm staying right here.
Who will be our halfway leader and what will that score be? Will Phil and Rory slide away?
Text us your US Open thoughts on 81111 or Tweet #bbcgolf
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Patrick Reed thinks a lot of himself. In March 2014, after winning only his third Tour event, he pronounced himself as one of the world's top-five players.
Bold. But maybe correct.
He is up to 15 in the world in the latest rankings, rising fast and he has been remarkably consistent tee to green so far at Chambers Bay.
He has found 18 of 20 green in regulation so far - 90% success rate and clear of the field.
Reed in the lead
Cole Hammer, the 15-year-old who was born this century - I know - launches his drive down the first. He is starting on +7 and needs a minor miracle to extend his stay. I'm not sure he'll be too fussed if he doesn't.
Up on the second Patrick Reed knocks in for birdie and he joins Henrik Stenson and Jordan Spieth at -5.
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Henrik Stenson bisects the 13th fairway - it's the widest on the course at 105 yards. Rory McIlroy is wayward with his tee shot on the par-three third but he is at least on the green - it's 50 feet plus for birdie and his attempt does not threaten the hole. A tough eight-footer for par coming up.
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Colin Montgomerie showing terrific course management on the short par-four 12th. Rather than taking on the 284-yard hole, he lays up shot and fires a wedge to five feet.
Phil Mickelson is up on the elevated 15th tee looking down towards the green 144 yards away and the Puget Sound water behind it, glistening in the sunlight. It's all rather pleasant. Except Mickelson's ball plugs in the bunker protecting the front edge.
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The last men out of the hutch are away. Among them is Rich Berberian Jr. The American was 156th and last after round one following a 13-over 83. Northern Ireland's Darren Clarke, who is currently last, will be watching his progress with interest one would imagine.
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Rory McIlroy's birdie attempt on two stays up but par will do. Phil Mickelson knocks in his five-footer but that's two dropped shots in his first five holes and he is back to one over.
Dustin Johnson knocks in his bogey putt on three and we have just two joint leaders. Jordan Spieth is safely in the clubhouse on five under. Henrik Stenson has 15 holes to play.
Mickelson magic
Dustin Johnson will be dropping at least one. His first shot out of the bunker ends up back in the sand. His third finds the green but he's got half a dozen feet to just go four under.
Back on 14 and Phil Mickelson plays the kind of shot only Phil Mickelson can play. He is only five yards from the flag but his ball balloons about 20 feet in the air before coming to rest short of the hole. He then stumbles back into the bunker. Bogey putt coming up.
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Dustin Johnson about a yard from perfect with his tee shot on the third. But rather than kicking down left off the bank, his ball trickles back towards a bunker, gathering pace with each revolution before it comes to rest in the sand.
Phil Mickelson playing scratchy golf on 14, his approach to the green gets caught up between the rough and sand aside the green.
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Phil Mickelson in a spot of bother on 14, in a fairway bunker and he can only wedge out.
The projected cut mark has been brought in to +3. That puts the likes of defending champion Martin Kaymer in trouble. He bogeyed his opening hole and is +3.
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BBC Scotland's Tom English: Tiger Woods: It's like watching Shakespeare struggling to write a note to the milkman. Uncomfortable viewing.
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Dustin Johnson's birdie putt doesn't have the legs so he stays at five under. Phil Mickelson misses another birdie chance on 13.
On the 11th and more magic from Monty who fires right from the fairway and uses the contours to bring his ball to within 15 feet.
Over on three and Graeme McDowell, who is five over par, has a tap-in birdie after his tee shot on the par-three hole scoots round the back of the green, flirts with the bunker and ends up inches from the cup. A staggering shot.
Birdie for Rory
Rory from below the green on one and that's a decent chip to around 15 feet. Birdie chance coming up. And he drains it. An early move by the world number one who gets to one over. Up on the second, Dustin Johnson finds the heart of the green in regulation.
Over on 11 Henrik Stenson knocks in a short par putt to stay five under.
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James Richards: My money is on Stenson for clubhouse leader after round two
Bubba frustrated
On the 13th Bubba Watson, looking like a tub of raspberry ripple ice cream, fires at the flag. It must have looked good from where he was - the ball slipped no more than a couple of inches past the hole but it just would not stop and rolled to the back of the green, 30 feet by.
"Wow," mutters Bubba as he strides after it. "I must be the only man to hit eight iron into this green (the 13th is a 550-yard par four) and even I can't get it to stop."
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Maybe the bookies know something. Monty tugs his birdie putt before hurriedly knocking in for par. A big opportunity missed.
On the first, Rory McIlroy is out with a three-wood and hacking out of the rough and his ball shoots forward and trundles down to the left of the green. Dustin Johnson just made par from down there and I think Rory would settle for that too.
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Phil Mickelson misses his birdie putt on 12 but is safely in for par to stay level. Henrik Stenson also in for par on the 10th to stay five under.
Colin Montgomerie was 500-1 at the start of play yesterday. How good do those odds look at this very moment? The Scot has just nailed a hybrid on the 10th to six feet. An opening birdie?
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Back on the tee and defending champion Martin Kaymer of Germany finds the fairway. He is starting at two over. That's the same as playing partner Rory McIlroy who goes down the left edge and his ball snags in the cabbage. He may struggle to get up in two from there.
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On the first, Sergio Garcia asks his ball to go right and it obliges, staying away from the nasty slope that has taken many a ball way down left of the green. He has a monster putt of what must be approaching 100 feet. Adam Scott goes further right and is rewarded as the ball bounds down off the hill to 40 feet shy.
Dustin Johnson is also imploring his ball to stay right. It doesn't and skips down were many before have gone.
Monty finds the fairway
The completely unique swing of 2003 US Open champion Jim Furyk sends his ball careering down the 10th fairway. He is followed by Miguel Angel Jimenez and Colin Montgomerie. The 51-year-old Scot rolled back the years on Thursday to card a one-under 69. Another one of those today will do very nicely thank you. He is safely down the middle.
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Brandt Snedeker, playing with Stenson, comes in from the right of the green and his ball curls to a stop eight feet the other side of the hole.
Over on the first, which is playing as a par five today, Matt Kuchar flips a wedge onto the green and he's got a 20-footer for birdie. He misses it but has a straightforward one to stay three under.
On the 12th, Mickelson comes up 20 feet short with a putt from the off the front of the green.
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Over on the 10th the other co-leader, Sweden's Henrik Stenson, is also away with a drive to the fairway and his second on the par four skips 10 yards past the hole and up a little slope which returns the ball to within 10 feet of the flag. Big birdie chance first up.
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Joint leader Dustin Johnson gets his second round under way and he's a little fortunate not to find a fairway bunker. Playing partners Adam Scott and Sergio Garcia are also cleanly away.
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Back on the 11th and both Mickelson and Bubba leave their birdie attempts on the green. Tap-in pars and off to the 12th tee we go.
Spieth's spiel
Here's our joint leader Jordan Spieth on his round: "Two under each day is a goal that I want to do. My putter was on today, my driver wasn't but when your putter is on you can salvage a round. This is golf's toughest mental test. It's about testing patience. If my putter continues to stay hot we'll be in good shape."
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At least Tiger will not be last. At the moment, that dubious honour belongs to 2011 Open champion Darren Clarke. The Northern Irishman had a 10-over-par 80 on Friday to finish +17.
Tiger Woods misses cut
We skip back to the ninth to see the end of Tiger's round and it's an untidy finish. A snaking 40-footer slides four feet by and the par putt lips out. It's another bogey for the world number 195 and he ends with a six-over 76 and +16 for the tournament. And that folks, is the end of his involvement in this tournament.
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Back on the ninth, Justin Rose two-putts for par and the Englishman is signing for a level-par 70 - that triple bogey seven on the seventh being his downfall. Still at two over for the tournament, he's far from out of this.
Back on the second and Phil Mickelson finds the green with his second shot but he's got a 30-footer for birdie. Playing partner Bubba Watson follows Phil's line out right of the flag and his ball picks up more pace off the hill and he's left with a more makeable dozen feet for birdie.
Latest scores
-5 Spieth (US) F, D Johnson (US) Stenson (Swe) -4 Grace (SA) F, Martin (US) 17, Reed (US). -3: Luiten (Ned) F, Finau (US) F, Summerhays (US) F, Kuchar (US)
Selected others +1 P Casey (Eng) F: +2 Westwood (Eng) F; Rose (Eng) F; +4 Donald (Eng) F +5 Poulter (Eng) 17 +15 Woods (US) 17
Projected cut: +5
For a full leaderboard, click this way.
Mickelson back to level
Peter Scrivener here to take you through the next couple of hours.
And I start on the 10th hole with Phil Mickelson immediately dropping back to level par. A poor second shot that missed the green proves costly, although Lefty's short par putt looked makeable. He's got 17 holes left to make inroads into the lead.
Spieth into lead at -5
Jordan Spieth's putting today deserves a slice of lead pie and that is exactly what he is getting.
He drains from eight to 10 feet on the final green of his round. That takes him to five under and back to the top of the leaderboard, alongside Henrik Stenson and Dustin Johnson who are yet to start their day's work.
Day done on -2
Jason Day is wobbling like he has taken a uppercut on the chin. Or sunk 12 Saturday-night pints.
I'm not surprised the Australians' vertigo was triggered as he made his way down from the crow's nest of tee down to the ninth green far below. It is really steep.
He regains his footing to splash out of the sand to within ten feet. Par putt next. A little shakily, it slips by. Four feet for bogey. In she goes and he is done at two under.
Westwood done on +2
Lee Westwood has signed off on his round in very ugly style.
A triple bogey seven on the 18th leaves him the wrong side of par on two over.
Shame. A damn shame.
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Day's collapse came right in front of the grandstand on the ninth. Jordan Spieth shows some nice empathy, telling some rubber-necking spectators to put away their camera phones.
Spieth has hit a nice approach by the way and has a birdie chance.
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We have a problem out on the ninth.
Jason Day is in a crumpled heap on the fairway. It looks like he has collapsed rather than fallen. He suffers from vertigo and that is being pinned as the likely cause.
Medical attention has reached him already and he is sitting up and talking with the doctors.
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Two things to mention as Phil Mickelson, Bubba Watson and Angel Cabrera tee off together.
First, someone shouts "get in the hole" on a par-five opener like a trained gibbon.
Second, the announcer practically gives Mickelson and Watson's zip codes, namechecking their home town and state. Cabrera is just "from Argentina". A chance to impart a much-needed geography lesson missed.
Grace finishes -4
Branden Grace has a real ogre of putt to contend with on the last. This is for par. It draws round, but not enough.
He makes the four-footer coming back to clock off with a three-under round for the day, four-under overall.
Our leaderboard is almost back to as you were. Overnight top dogs Dustin Johnson and Henrik Stenson have just Ben Martin for company.
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Jordan Spieth with the touch of a butterfly-collecting brain surgeon as he scoops a lovely little chip up to within five feet on eight for a birdie chance.
Nope. The ball slips by.
Poulter back to +5
The halfway snip of the field is going to take out Ian Poulter as it stands.
The Englishman dropped two shots on six and is five over. He has three holes to smoke out the birdie that will extend his stay at Chambers Bay.
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Ben Martin has been consistency personified today. A bogey six at the first, but since then it has been all pars with three birdies thrown in.
That has been been rewarded with a share of the lead. He has never made it beyond the first two rounds before.
He is going to today. The cut is projected to fall at five over by the way.
Latest scores
-5 Grace (SA) 17, Martin (US) 15, D Johnson (US) Stenson (Swe) -4 Spieth (US) 16, Reed (US). -3: Luiten (Ned) F, Finau (US) F, Summerhays (US) 17, Kuchar (US)
Selected others: -1 Westwood (Eng) 17; +3 Rose (Eng) 16;+1 P Casey (Eng) 17; +4 Donald (Eng) F +14 Woods (US) 16
For a full leaderboard, click this way.
Spieth & Summerhays drop back. Grace into joint lead
Jordan Spieth cannot dust up the scrapes on the seventh. His round is dented by a bogey, three-putting after perching himself in a nightmare position over the hole with his initial approach.
Spieth's place among the front runners is taken by South African Branden Grace with a birdie on the par-three 17th.
And Daniel Sumerhays hits trouble. A double-bogey six on seven has him back to three under.
Rose to +3
Justin Rose's round has just gone into reverse.
That tricksy little minx of a seventh is to blame again.
The Englishman picks up a triple bogey seven and is back to three over.
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Jordon Spieth on the par-four seventh has a pretty much unputtable birdie chance. He is knocking along a precipice, down a steep slope. It runs about 12 feet by and he will be pretty happy with that...
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Freight and passenger trains still chug through Chambers Bay with the tracks running right alongside the 16th and 17th fairways.
If Justin Rose landed his drive on a passing express train, he could have had a tricky second shot from Canada.
The Englishman didn't. He is level par overall with three holes to play.
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Rory McIlory touches the peak of his dazzling white cap as he is cheered out to practice by some of the patrons. Actually his outfit is pretty much all white - he looks like he is fresh out of a washing powder advert.
The Northern Irish young gun - two over - gets going at 22:28 BST.
Westwood to -1
Lee Westwood has struck birdie juice.
The man from Worksop has sunk a long snaker of a birdie putt on the par -three 15th. That is his sixth in nine holes.
He is four under for the day, one under overall.
Latest scores
-5 Summerhays (US) 15, Spieth (US) 15, D. Johnson (US), Stenson (Swe) -4 Grace (SA) 15, Martin (US) 13, Reed (US). -3: Luiten (Ned) 17, Kuchar (US)
Selected others: -1 Westwood (Eng) 15;E Rose (Eng) 15;+2 P Casey (Eng) 15; +4 Donald (Eng) +13 Woods (US) 14
Holmes back home on two under
J.B Holmes on the last with a piddly little putt for a birdie and three under.
Snatched at it! It whips clean by and instead he has an awkward four footer back for par. A long, hard look at it...In he comes...and down it goes.
A very impressive four under for the day for the American.
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Joint leader Daniel Summerhays tells his caddy he would be happy to land in the front of the greenside bunker as he stands over his second in the wild stuff on the par-four seven.
Seemed pessimistic, but that proves about right.
He undercooks and rolls back 40 yards. Them's the breaks on Chambers Bay. Plenty to do from there for par.
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Dutchman Joost Luiten is getting his feet under the table.
Successive birdies on 15 and 16 shift him onto one under for the day and three under overall.
Alongside him in a share of eighth is Matt Kuchar.
Oh I say! A moment of magic off the face of Ian Poulter's sandwedge as he chips in from the sand for a birdie on four. Three over for the Postman.
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Jordan Spieth's putter is red hot and its owner is ice cool.
His par putt on five - a tricky eight-footer made all the more difficult by the roller-coaster greens - disappears down the chute.
He keeps his share of the lead.
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Lee Westwood is posting some nice numbers.
Birdies on seven and eight are followed by more on 10 and 12. Two under for the day and one over overall.
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Jordon Spieth plays golf better than he swears.
The American plunges his second shot into a greenside bunker on the par-four five and responds with "Dang it Jordan!".
Still five under and with a share of the lead though. And that is a decent recovery shot from the sand. He has a chance of keeping up top of the leaderboard.
Tiger Woods has had a wobble with bogies on two and three taking him to three over for the day and 13 over overall.
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A less kind man than me might suggest that Miguel Angel Jimenez looks increasingly like he is starring in a Spanish remake of Gregor Fisher's 90s sitcom "Baldy Man".
And he is still the coolest man in golf by a country mile.
He has arrived on the course and will begin his round at 22:28 BST.
Phil Mickelson is also in the house. He will be hunting the one Major not on his mantelpiece from 21:33 BST.
Get involved via #bbcgolf
We have the first punt on how many Majors Jordan Spieth will be able to tell the grandkids about winning once he has hung up his spikes.
TheSultan: "Spieth gets fewer than McIlroy. McIlroy 10, Spieth 7 or 8."
Your guess is welcome on #bbcgolf and 81111 on text.
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Jason Day gets digging in a bunker at four.
The Aussie's ball looks like a comet crashed in the moon, leaving him a shot out of a dirty great crater in the grey surface of the sand.
He escapes with a bogey five, which is not too shabby. He is back to two under.
Grace back to -4
Daniel Summerhays with a chance to take an exclusive hold of the lead with a birdie putt at five? But it slides and he stays at five under.
Branden Grace has dropped straight out the backdoor, missing his par putt at 13 to slip back to four under.
Grace into a share of the lead
Branden Grace? Come on down!
The South African makes it a party of five at the top of the leaderboard with a birdie three at 12.
Jordan Spieth, Daniel Summerhays, Dustin Johnson and Henrik Stenson are already sipping the rare atmosphere in the big-chance saloon.
Clarke suffering
Darren Clarke is rock-bottom last, propping up all 155 others in the field. His scoreboard is a horror show - starting with a triple-bogey seven and featuring another seven dropped shots.
Two birdies have repaired some of the damage, but not much. He is 15 over for the tournament, eight over for the day.
Overnight joint-leader Henrik Stenson strolls into Chambers Bay looking as cool as a cucumber, even with a television camera poking in his face.
The Swede smoothes down his eyebrows Fonz-style with a wipe of a wetted finger and points down the lens. Nice.
Summerhays into a share of the lead
And then there were four...
American Daniel Summerhays acknowledges the cheers from the crowd as he sinks a birdie putt on four to move into a share of the lead alongside Jordan Spieth and clubhouse-bound pair Henrik Stenson and Dustin Johnson.
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Australian Jason Day - a man with skills to win a major, but perhaps not the mentality - is showing up nicely.
After picking up birdies on one and two, he holes a knee-knocking five-footer on three for his par.
He is one under for the day - three under overall.
Get involved via #bbcgolf
If you want to get in touch with this live text, we are just a text, tweet or social media musing away.
#bbcgolf,81111 on text from UK mobiles or the BBC Sport Facebook page are the details you need.
To start, anybody fancy a quick guess on what spread you would get for Jordan Spieth career Majors?
North of five, south of ten? What do you reckon?
Cloudless in Seattle
It is a sparkling day in Seattle by the way. Fine sunshine and a breath of wind, but not too significant.
Nothing to complain about meteorologically for the players.
American Daniel Summerhays - playing in only his second US Open - has moved into a share of second by the way.
Two birdies in his last three holes to move to four under. Six left in his round.
Out of the Woods?
Ah, yes Tiger, Tiger.
Not so much "burning bright" as "playing somewhat less than alright" yesterday.
He scored a 10-over 80 yesterday - the lowlight of which was a triple-bogey seven on 14.
He has steadied the ship so far today - plugging away at one over for the day after 10 holes.
Latest scores
So this is where we stand, as we stand.
-5: Spieth (US), D. Johnson (US), Stenson (Swe) -4: Grace (RSA), Martin (US), Reed. -3: Lovemark, Summerhays, Kuchar (all US)
Selected others:-1 Rose (Eng) +1 Westwood (Eng) +4 Donald (Eng) +12 Woods (US)
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Hang on! Birdie four at the first and Jordan Spieth is back at the top of the leaderboard again, sharing the spotlight with overnight leaders Henrik Stenson and Dustin Johnson who are yet to start their second rounds.
Full scoreboard coming right up...
Master of the course
One man who didn't hang around to dish the dirt on the course is Jordan Spieth.
The Masters champion just gets on with scoring low as a limbo dancer's shoulder blades.
He is the headline-maker so far in the second round of the US Open.
He started like a train, scoring four under for his first eight holes to take the lead on six under.
He has slipped back with a double-bogey six on 18, but is the main mover and shaker so far.
" You wouldn't walk your dog that far."
Well, Robert Trent Jones Jr - the course architect behind Chambers Bay - got the passion and emotion bit from US Open class of 2015.
However some of them felt like that had walked into a Jackson Pollock mess rather than a masterpiece.
"Extremely poor". "As bad as they look." " You wouldn't walk your dog that far."
Those were three of the critical notices handed in by the field after the first round of the US Open.
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"What I want this course to do is to move the golfer to want to play.
"I want to evoke passion and emotion and finally art.
"You have walked into a piece of fine art. You the golfer have become part of the dance of life, part of the game."