Tiger Woods put aside worries over his father's health to take the joint lead at the Deutsche Bank Championship near Boston with a first-round 65.
FIRST ROUND LEADERBOARD
US unless stated
-6 T Woods, R Palmer
-5 M O'Meara, C Beckman, J Byrd
-4 B Mayfair, C Perks (NZ), C Howell III, J Rollins, D Papas (SA)
Level J Rose (GB), P Price (GB)
Earl Woods, who first taught the world number one to swing a club, has suffered a relapse of prostate cancer.
Woods admitted his father's condition had been playing on his mind prior to this week's tournament.
But his six-under par round, matched by fellow American Ryan Palmer, put him a shot clear of three other players.
Mark O'Meara, Cameron Beckman and Jonathan Byrd all posted 66s, with a group of five a further shot back.
Only a missed 12-foot birdie putt on the ninth hole - Woods' last - prevented him from taking sole possession of the lead.
Woods, who could see his record 264-week streak at number one end this week if Vijay Singh finishes ahead of him, has just one win from 16 PGA Tour starts this year.
Singh - a five-time winner this season - shot a three-under 68 in the morning, but Woods went out and collected seven birdies against just one bogey.
"It's certainly nice that I don't have to go out there and shoot a round like this just to try and make the cut," Woods said.
It is the first time Woods has held a first-round lead since he won the 2003 Western Open.
He has won eight of the last 10 tournaments when he's led or shared the lead after he first round.
Woods is playing his last event before the Ryder Cup, having opted to miss the forthcoming Canadian Open.
Earl Woods was initially diagnosed with prostate cancer six years ago, but radiation treatment was believed to be successful.
Woods senior said on Wednesday that the cancer had returned and spread throughout his body, forming lesions in his back and a tumour behind his left eye.
But he added that the tumour has been eradicated by further radiation and he is feeling better, much to Tiger's relief.
"It's been tough," said the world number one. "It's just like it was back in '96 and
'97, when my dad had a heart attack and had complications with heart surgery."