Overnight leader Sergio Garcia struggled to a 3-over-par 73 on Thursday and shares second place with K.J. Choi (71), Tim Herron (72) and Rocco Mediate (72). The group completed 36 holes at 2-under-par 138.
Woods began Friday's second round two shots behind Garcia but did not make a move early. He was even through his first four holes but his fortune changed at the 315-yard, par-4 fifth hole.
The No. 1 player in the world drove the green at the fifth and two-putted from 20 feet for birdie. He added a 10-footer for birdie at six and found himself tied for the lead with Garcia, who would fall down the leaderboard thanks to three consecutive bogeys from the sixth.
Woods drained a 17-foot birdie putt at the eighth and tapped in a four-footer for birdie at No. 9 to take a big lead over the field. The defending champion did his best to save bogey at the 10th after he missed the green. From an awful lie, Woods pitched 50 feet past the hole into the rough on the opposite side of the putting surface. He chipped to three feet and sank the bogey-saving putt.
At the par-5 12th, Woods roped a 2-iron on to the green with his second shot but left himself with a long eagle try. He left his first putt seven feet short but canned that putt to reach 7-under par for the championship.
Woods mis-clubbed at the 220-yard, par-3 15th when his 5-iron came up short in a bunker. He could not get up-and-down for par but rolled home an eight-footer at the last to go five clear of the field.
'It's awfully nice to be in front,' said Woods. 'You have those shots to kind of play with. I've always said I'd much rather be in front than trying to make up shots from behind because if you don't get off to a good start you're further behind.'
Woods, who also won this event in Spain in 1999, is still in the hunt for PGA Tour Player of the Year but could use a win this week. He has four titles in 2003 and with a win on Sunday, he would have more wins than anyone on tour, and depending on what Vijay Singh, the current money leader, does this week, Woods would top the money list.
All of those accomplishments and Woods failed to capture a major championship for the first time since 1998.
'With a few tournaments to go, I'm sure I would have just a slight edge,' admitted Woods, who has won the award every year since 1999. 'It's going to come down to this event and the Tour Championship.'
Garcia's round fell apart starting at the sixth as he missed three consecutive par saves from inside 10 feet. The young Spaniard traded a pair of birdies and a pair of bogeys over the second nine to finish in the tie for second.
'I just couldn't hole the putts today,' Garcia said. 'That was the biggest difference. Tiger was making them and I wasn't.'
Choi was in good shape but bogeyed two of his final five holes to fall back into the group.
Mediate tallied two birdies, two pars and five bogeys on his front nine but became Woods' closest competitor with four straight birdies from the ninth. Mediate dropped shots at 15 and 18 and lost sole possession of second.
Herron mixed four bogeys and two birdies throughout his round.
Stuart Appleby shot a 2-under 68 on Friday and is tied for sixth place with Spain's Ignacio Garrido, who posted a 1-over 71 in the second round. The duo is tied at 1-under-par 139 and is one ahead of Singh.
Masters champion Mike Weir, who is also in the running for Player of the Year, carded a 3-over 73 and shares ninth place with 2001 U.S. Open champion Retief Goosen (69), Jonathan Kaye (69) and Jerry Kelly (72). That group is at 2-over-par 142.