Tournament host Tiger Woods had two eagles in a five-under 67 on Friday to seize a three-shot halfway lead in the $5 million Chevron World Challenge.
Woods, the 14-time major champion who is seeking his first victory in more than two years, had a 36-hole total of eight-under par 136.
Overnight leader KJ Choi and American Matt Kuchar shared second on 139. Zach Johnson and Hunter Mahan were tied on 140, Johnson carding a 67 that included six straight birdies from the sixth hole and Mahan a 68.
South Korea's Choi started the day with a three-shot lead and managed to keep his nose in front for much of the day. He was undone, however, by a quadruple-bogey seven on the par-three 15th.
Choi managed to bounce back with a birdie at the par-five 16th, his one-over 73 good enough for a share of second after Kuchar -- who teamed with Gary Woodland to win the World Cup for the United States in China last week -- bogeyed 18 for a five-under 67.
The biggest blot on Woods' card was his own double-bogey on 15, where he was in the water off the tee.
Woods eagled two par-fives, the second and the 11th, and had five birdies and two bogeys on the Sherwood Country Club layout.
His score could have been better if not for a few missed putts, including three from within four feet.
"That was probably the highest score I could have shot today," Woods said. "I hit the ball really well and hit one bad shot today and almost made birdie on that hole, if I would have hit a decent putt. Hit a few bad putts today but overall I really hit the ball well all day."
Woods' position atop the leaderboard marks his second successive stroke-play start in which he has led heading into the weekend.
He also topped the leaderboard after 36 holes at the Australian Open last month, eventually finishing third behind Greg Chalmers.
The last time Woods held the lead after any round on the US PGA Tour was at the Barclays in 2010, where he shared the first-round lead and eventually finished 12th.
"Well, I want the lead after the four days," Woods said. "Two days is nice, but four days is even better. I know I'm playing better, and it's nice to see my position on the leaderboard kind of equating to it."
Woods, who started the day three shots off Choi's lead, shaved two strokes off the South Korean's advantage with an eagle at the 531-yard second hole, where he hit his five-iron approach shot from the hillside rough to four feet.
A birdie at the next hole saw him grab a share of the lead, but a birdie at the fourth from Choi put the South Korean back in front.
Choi's lead was back to three strokes when he birdied the par-four sixth and Woods three-putted for bogey.
Woods had closed the gap to one stroke through 10, then rolled in a 15-footer for eagle at the 517-yard 11th, where Choi's birdie left them tied for the lead.
"At 11, I hit a good drive and I hit a four-iron," Woods said. "The wind was going back and forth all over the place out there and it was four-iron, five-iron, four-iron ... it came out perfect, just a nice, high softie in there, and made about a 15-footer."
Woods birdied the next two to take the outright lead for the first time. He admitted it felt strange to come away from his double-bogey at 15 with his lead over playing partner Choi doubled to four shots.
"Not exactly how I envisioned it, increasing my lead," said Woods, whose tee shot hit the rocky pool in front of the green. "I hit a sweet shot in there. Unfortunately I caught the wrong gust at the right time."
Choi said wind contributed to his own big number at 15.
"The tee shot went into the water, third shot went into the water again, got a fifth shot over the green, chipped it and made the putt," he said. "I think it was really misjudgment on the wind on the tee shots."
Kuchar, meanwhile, had his eye on the leaders as he put together his five-under effort that included seven birdies.
"They were going good," Kuchar said. "I saw 10-under and eight-under. I knew I was at six-under and I knew that wasn't out of it... with 36 holes to play I've got some time to catch up."
Choi was also pleased to be in contention.
"We still have a lot of holes remaining," he said. "My body is a little fatigued right now. I just need to get my condition back. There's still a lot of holes to play, so I'm looking forward to it."