France's Gregory Bourdy and India's Jeev Milkha Singh lead the Irish Open after seven-under-par 65s on the opening day at Royal Portrush.
They lead by one from a group of six which includes England duo Andrew Marshall and Mark Foster.
Defending champion Simon Dyson is two behind on 67 while Rory McIlroy dropped a couple of late shots in his 70.
Padraig Harrington is well placed on five under after an opening day which saw a 105-minute storm delay.
World number two and local favourite McIlroy, who bogeyed the 16th and 18th, said: "After a two on 14 I was thinking I could get a really good score if I could pick up one or two shots.
"It was a round which should have been better.
"It was a sloppy finish and hopefully I can pick up those shots early [on Friday]."
Northern Ireland's three Major champions McIlroy, Darren Clarke and Graeme McDowell, were the big attractions at the first European Tour event to be sold out for all four days.
The huge galleries saw the bulk of the good scoring achieved in the morning before the weather took a turn for the worse on the north coast of Northern Ireland.
McDowell was the first of the three local heroes into action, and he pitched into bushes for a double-bogey seven on the long 17th during his one-under 71.
Clarke bounced back from a run of three successive bogeys on the front nine with three birdies coming in to record a 71.
Harrington, playing with McDowell, pitched in from around 60 yards for birdie on his penultimate hole and with a 67 is well in the hunt.
Ryder Cup captain Jose Maria Olazabal and Scot Paul Lawrie - playing together for the third time in under two months - both shot 69.
Another former Open champion, American John Daly, was out in the first group and returned a 71.
England's James Morrison claimed the car on offer for a hole-in-one at the 210-yard 14th, known as Calamity Corner.
Play was suspended just after 15:00 BST with storms on the way and the threat of lightning causing concern, but the event resumed later in bright sunshine.