Little-known Briton Graeme Storm upstaged the game's biggest names by charging into an early two-stroke lead in the opening round of the U.S. PGA Championship.

The 29-year-old Englishman, who won his first European Tour title six weeks ago at the French Open, fired a flawless five-under-par 65 in sapping heat at Southern Hills Country Club.

Playing in his eighth successive tournament, Storm set the tone for the day with three birdies in his first four holes before ending it two ahead of twice major champion John Daly.

"It was just one of those rounds when I never really thought about anything," Storm, the 1999 British amateur champion, said.

"I just kept on doing the things that I was trying to do, which was just enjoy myself.  I did get off to a fast start and I nearly had a hole in one at the 11th, which was my second hole."

Arron Oberholser shot a four-birdie 68 to finish level with fellow American Woody Austin, three ahead of defending champion Tiger Woods who bogeyed two of his last three holes for a 71.

British Open champion Padraig Harrington, boosted by three birdies in a row, was among a group of seven bunched on 69, along with Colombia's Camilo Villegas, 2006 U.S. Open champion Geoff Ogilvy of Australia and Britain's Lee Westwood.

"Obviously since I've won at the Open, things have moved very quickly," said the Irishman.  "There was a lot to do at home. Last week there was still things going on. This week there's still things going on.

"The benefit is the fact I've won a major. You feel like you've won one, you can win two, you can move on from that.

"So there's a certain level of confidence. And I also feel that there's a certain level of adrenaline coming on from having won, and a certain high from it."

Harrington overcame erratic play off the tee by muscling balls out of the Southern Hills rough and on to greens five times in a round including four birdies and three bogeys.

He feels he is striking the ball well and doing a good job of focusing on the job at hand.

"When good things happen to me, I tend to keep my head down, put the blinkers on and keep going forward," he said.

Harrington had taken his score to two under par before registering a bogey at the par-four 17th.

"I'm in good position," the 35-year-old Dubliner said. "But it's how I play the next three rounds."

Storm, who worked in a cream cake factory after losing his European Tour card in late 2002, raced to the turn in four-under 31 before chipping in for his final birdie of the round at the par-four second.  He parred the last seven holes to maintain control in the final major of the year.

Daly, a notable absentee from Southern Hills Country Club in the build-up, birdied four of his first 13 holes to set the early first-round pace.

The big-hitting American, who became one of the most unlikely major winners of all time by clinching the 1991 PGA Championship at Crooked Stick, was delighted with his start.

"It was one of those rounds where I was very aggressive off the tee," the 41-year-old said after mixing four birdies with a lone bogey. "I didn't know what else to do.

"I haven't played this course since '94 and didn't play a practice round this week because it was too hot. But the angles were really good for me today and I hit the driver real well."

Daly, who has made only five cuts in 17 PGA Tour starts this season, said he had no idea if he could maintain his form for the rest of the week.

Three-times champion Woods, who racked up four birdies and five bogeys, felt he hit the ball better than his scoring indicated.

"That's a good sign heading into the next three days," said the world number one, who is desperate to win his first major in 12 months. "I just need to clean up my round a little bit.

Of the other big names in the 153-strong field, Retief Goosen and Sergio Garcia opened with 70s, Ernie Els a 72 and 2005 winner Phil Mickelson a 73.