Australia’s Adam Scott has endured a mixed opening round of the US PGA Honda Classic as Rory McIlroy seized the clubhouse lead with a bogey-free seven-under par 63.

McIlroy sank a 27-foot birdie putt at the second at Florida’s PGA National on Thursday and had a tap-in birdie at the par-5 third for a solid start to the $US6 million tournament.

The world No.8 from Northern Ireland then opened the back nine with three birdies in a row, before sinking two more at 17th and 18th.

Scott, in his first tournament after a six-week break, carded five birdies and three bogeys to finish with a two-under 68.

He remains five shots off the pace in a tie for 21st, with play still underway.

Tiger Woods, playing for the first time in a month, was eight shots behind after a 71.