Sweden's Carl Pettersson headed the USPGA Championship field halfway through the first round.

Pettersson shot a bogey-free round of 66 to hold a one-shot lead over Rory McIlroy of Northern Ireland and American Gary Woodland.

Like Pettersson, McIlroy didn't blot his copy book once, although he feels the favourable conditions - which replaced the thunderstorms found earlier in the week - had a part to play in that.

"I think that's my first bogey-free round in a while and it was a great way to start," said the 23-year-old.

"I'm pretty comfortable on the course and only played nine holes on Monday and nine on Tuesday - I didn't feel I needed to play more.

"I'm expecting this to be the best day of the week (weather-wise), but it's hot and you just try to stay hydrated."

John Daly and defending champion Keegan Bradley headed a group a further shot back on four-under-par.

Former world number one Tiger Woods and Adam Scott, who fluffed his lines so badly in the closing stages of The Open, started with solid 69s.

One of the day's later starters, K.T Kim of South Korea, looked in with a shot of bettering Pettersson's mark after he took the turn on three-under.

Golf 365