Darren Clarke fired a six-under 66 on Thursday to take the 18-hole lead at the Regions Tradition major in Birmingham, Alabama.
Starting on the tenth hole, Clarke birdied five holes on his front nine to take a one-shot lead over Jerry Kelly and Stephen Ames, who both carded 67s at the Greystone Golf & Country Club.
Defending champion Steve Stricker is tied for fourth with two others after shooting a 68. He's joined by Alex Cejka and Mike Weir at four under. Seven players are tied for seventh on three under.
The event is four rounds and the purse is $2.4 million.
Clarke birdied his first two holes to make the turn at five under. He carded two more on his round before a bogey at the par four eighth hole.
"All in all, six under par is a pretty decent start," Clarke said, adding that there's the added excitement of playing in a major.
"Majors are majors, it doesn't make any difference which tour they're on. You want to play well," Clarke said.
"You ask Tiger Woods, you ask Rory McIlroy, you ask Dustin, you ask Mr Nicklaus, you ask anybody, majors are what they all want, and it's the same out here. We all want them, too.
"There's a little bit of added excitement, four-round tournament. I think it's the first tournament I've walked since Pebble Beach last year, so my legs are a little bit sore. Going to go down to the range, do a little bit of work and then relax and get ready for (Friday) again," he said.
Kelly came out of the gate strong with four birdies in his first five holes. He bogeyed the sixth but played clean golf the rest of the way, adding two more birdies.
"I love tree-lined golf courses. Even if they're wide, it gives me that alleyway to shoot it down. It would be kind of like a bowler having lanes 15 yards wide," Kelly said.
"I don't know if they could really throw the strike off the edge of the lane like they do. That's kind of the way I am on big, wide open courses, I don't have any parameters. So put me in some trees, I love it."
