Tiger Woods fired a 9-under 61 on Friday and jumped seven strokes clear of the field after two rounds of the WGC - Bridgestone Invitational.
Woods, who matched the course record with his 61 on the South Course at Firestone Country Club, finished 36 holes at 13-under-par 127. He missed his own 36-hole scoring record by two strokes.
He has won this event seven times already, and has four victories this year, including at the WGC - Cadillac Championship.
Defending champion Keegan Bradley posted a 68 to move into a share of second place at minus-6. He was joined there by Chris Wood, who also had a 68 on Friday.
Henrik Stenson (70) and Bill Haas (68) share fourth place at 5-under-par 135.
Jim Furyk, Luke Donald, Jason Dufner and Bubba Watson all shot 69 and are tied for sixth at minus-4.
First-round leader Webb Simpson struggled to a 5-over 75 and tumbled into a share of 16th at 1-under 139.
Woods got off to a flying start as he stuffed his approach at the first three feet from the hole. After knocking that in for birdie, he rolled in a 20- footer for eagle on No. 2.
The seven-time winner moved to 4-under after three holes as he converted a 13- foot birdie try at the third.
Woods drove against a tree on No. 6, but managed to save par from 22 feet out. He followed with a 3-foot birdie putt at the seventh, then carded pars at eight and nine.
At the 10th, Woods dropped his approach to seven feet and made that birdie effort. He followed with a 5-footer for birdie on the 11th.
Woods, who has never shot 59 on the PGA Tour, drained a 20-footer for birdie at 12. He made it four in a row at the 13th as he converted a birdie try from 14 feet out.
"I certainly could have done it. The good news is I've done it before. It's one of those things, where I felt pretty relaxed with it," said Woods, who shot 59 at Isleworth. "If I hadn't ever shot 59 before, it would have been a different story."
He needed two more birdies for 59, but was unable to make them. He saved par from eight feet out on 14 after driving into the right trees. Woods missed a 9-footer at 15, then knocked his third at the par-5 16th 30 feet behind the hole.
Woods 2-putted for par from there. He left himself six feet at the 17th, but failed to convert. At the last, he blocked his drive into the right trees and scrambled for a closing par.
"It felt really good (to shoot 61). I had it going today. It was a nice start. Four-under through three is a nice thing to have, and I just let the round build from there," Woods said. "I made a couple key putts for pars. I made a big putt at six and that kept the momentum going."
Bradley got off to a fast start as he birdied the 10th and 11th. After six pars in a row, he birdied the 18th, his ninth.
He converted another birdie effort at the second to climb to 8-under. However, Bradley stumbled to bogeys at four and seven to fall back to minus-6.
"My game feels really sharp right now, so everything that I've done this week so far has felt really good, putting, driving the ball, irons. I haven't gotten the most out of both my rounds, so hopefully tomorrow I can do that," Bradley stated.
Wood opened with a birdie at the first. He traded a bogey for a birdie from the fifth. The Englishman reeled off eight consecutive pars from the seventh.
He moved to 7-under with birdies at 15 and 16. However, Wood tripped to a bogey at the last to end six back.
NOTES: With inclement weather expected overnight and early Saturday morning, tee times won't start until 11 a.m. (ET) with players in threesomes off the first and 10th tees ... Woods' 61 matched his career best on the PGA Tour ... Woods has won 36 of the 46 times he's owned the 36-hole lead on the PGA Tour ... The largest 36-hole lead he lost was four strokes, which was at the 2009 PGA Championship. That was also the first time he coughed up the 54-hole lead in a major.