Match ends, Leyton Orient 0, Brentford 1.
Brentford won at Leyton Orient to go second in League One and boost their hopes of automatic promotion.
Marcello Trotta scored the only goal in first-half stoppage time with a powerful low drive from 20 yards.
James Tarkowski was sent off for two yellow cards but the visitors survived for 41 minutes with 10 men.
Brentford are a point behind League One leaders Wolves, who drew 0-0 with Shrewsbury, while Orient drop to third, two points behind the Bees.
The hosts enjoyed long spells of pressure in the first half, with striker David Mooney chipping over from the edge of the box and Dean Cox fizzing a shot wide from 25 yards.
Before Trotta's opener, his 12th goal of the season, O's goalkeeper Eldin Jakupovic had smothered Clayton Donaldson's attempt.
Brentford's task was made more difficult four minutes into the second half when centre-back Tarkowski, one of three players booked in a feisty first period, saw red after lunging in on Romain Vincelot.
But Orient, who have played two games more than their London rivals, struggled to make the advantage of the extra man count.
Moses Odubajo spurned the home side's best opportunity, firing straight at David Button from eight yards, while Shaun Batt's header was cleared off the line by Alan McCormack.
And they were lucky to escape further damage at the other end when Donaldson's goal-bound header ricocheted behind off his own player and on-loan winger Alan Judge struck a post late on.
Leyton Orient manager Russell Slade told BBC London 94.9:
"The effort and determination was of a high standard and that culminated in a strong first-half performance.
"We were unfortunate to go in at half-time 1-0 down. We should have closed it down better.
"We've come from behind before and I fully expected to put them under pressure. How we've not scored today, I don't know.
"It's a good group, I believe in them and we'll fight for as many points as we can."
Brentford manager Mark Warburton told BBC London 94.9:
"There was a lot at stake and both teams realised that. It was a big derby and second versus third.
"I'm delighted with the way the boys reacted to it. We tried to avoid being drawn into a melee and the key for us was focusing on what we do well.
"The players have learned from last year's disappointment and hopefully we're in good shape to keep pushing forward."
- 2OmozusiBooked at 69mins
- 3SawyerBooked at 41minsSubstituted forBattat 70'minutes
- 8JamesSubstituted forBartleyat 88'minutes
- 9LisbieSubstituted forDagnallat 75'minutes
- 26TarkowskiBooked at 50mins
- 4ForshawBooked at 53mins
- 18JudgeBooked at 86mins
- 9DonaldsonBooked at 40mins
- 29TrottaSubstituted forDeanat 51'minutes
- Robert Madley
- Shots on Target
Second Half ends, Leyton Orient 0, Brentford 1.
Nathan Clarke (Leyton Orient) wins a free kick in the attacking half.
Foul by Clayton Donaldson (Brentford).
Alan Judge (Brentford) hits the left post with a right footed shot from the centre of the box.
Foul by Romain Vincelot (Leyton Orient).
Adam Forshaw (Brentford) wins a free kick in the attacking half.
Substitution, Leyton Orient. Marvyn Bartley replaces Lloyd James.
Attempt blocked. Shaun Batt (Leyton Orient) right footed shot from the centre of the box is blocked.
Corner, Leyton Orient. Conceded by Tony Craig.
Alan Judge (Brentford) is shown the yellow card.
Shaun Batt (Leyton Orient) wins a free kick in the attacking half.
Foul by Alan Judge (Brentford).
Attempt missed. Adam Forshaw (Brentford) left footed shot from outside the box misses to the left.
Corner, Brentford. Conceded by Nathan Clarke.
Foul by Shaun Batt (Leyton Orient).
Jake Bidwell (Brentford) wins a free kick in the defensive half.
Attempt saved. Adam Forshaw (Brentford) right footed shot from the right side of the box is saved in the top centre of the goal.
Attempt missed. Jonathan Douglas (Brentford) header from the centre of the box is too high.
Corner, Brentford. Conceded by Scott Cuthbert.