U.S. Open winner Justin Rose, bouncing back from missing the cut at the British Open, shot 6-under 29 over his final nine holes for a 66 that left him one stroke behind Scott.
Webb Simpson, a former U.S. Open champ, also made a big charge. He was 7 under through his first 15 holes and flirting with the major championship scoring record before a bogey at the seventh — his 16th hole of the round — stemmed the momentum. He had one more birdie shot at the eighth, but missed a 10-footer.
Simpson finished with a 64, tying the course record but one stroke shy from the lowest round ever in a major.
"I was thinking about it coming down the last few holes," said Simpson, whose 136 total left him three shots back.
Martin Kaymer, who won the PGA three years ago after Dustin Johnson's dubious penalty, shot his second straight 68 to get into contention.
Woods made back-to-back birdies with putts inside 10 feet at the fifth and sixth holes, but he still had a lot of work to do in his bid to break an 0-for-17 drought in the majors.
The world's top-ranked player opened with a disappointing 71. By the time he teed off in the afternoon, there were 41 players between him and the top spot on the leaderboard.
Others ripped through a course that seemed very much there for the taking, the birdies falling into the cup at an alarming rate.
But Oak Hill still had some bite. Just ask Lee Westwood, who made a double-bogey at the eighth, then a bogey on his final hole for a 73 that knocked him off the board.
Early on, the dreary weather provided another chance to go right at the soft greens, the same sort of conditions that made the opening round seem more like a regular tour event than a test of major proportions.
"It's a course you can attack," said British Open champion Phil Mickelson, whose game wasn't up to the task. Lefty shot his second straight 71, leaving him nine strokes behind Scott and flirting with the cut line.
Defending PGA champ Rory McIlroy was headed to the weekend after bouncing back from a tough start Friday. He played his first 10 holes at 5 over, but closed with four birdies for a 71 that left him even for the tournament.
"I've just got to try to get off to a fast start tomorrow," said McIlroy, who won last year by a record eight strokes at Kiawah Island. "I need to shoot something in the mid-60s to give myself a chance on Sunday."