A rejuvenated Lee Westwood set the early clubhouse target on the opening day of the 96th US PGA Championship at Valhalla.
The Englishman compiled a six under 65 that was matched minutes later by American Kevin Chappell.
Westwood, who carded a closing 63 at Firestone Country Club on Sunday after missing the cut in his previous four events, looked to have squandered a good start when he covered the back nine in 33 only to run up a double bogey on the first.
However, the 41 year old bounced back with a birdie on the fourth and rattled in four more in succession from the sixth, ending his round in style by holing from 40 feet on the ninth.
Italian Edoardo Molinari was five under par with four holes remaining, while Dutchman Joost Luiten and England's Ian Poulter boosted their Ryder Cup chances with rounds of 68 and Colin Montgomerie returned a highly respectable 70.
"I wanted to represent the Champions Tour well and 70 is okay to start with," said Montgomerie, who qualified by winning the US Senior PGA Championship in May. "I drove the ball well and knew if I did that I could get round."
All eyes were on Tiger Woods after he declared himself pain free and said he was targeting a 15th Major, despite getting in just nine holes of practice after withdrawing from the final round of the WGC-Bridgestone Invitational with a back injury.
But the former World Number One struggled to a three over par 74.
Westwood, whose 65 eclipsed his previous lowest score in the US PGA - an opening 66 at Oak Hill last year - said: "Last week was a big week for me.
"Going into last week I felt like I had turned the corner. I was starting to swing it a lot better but that's no good unless you start converting it into low rounds. The first three rounds were frustrating because I played a lot better than three over.
"Then obviously I got it going the final day, shot 63. I tried to keep it low key in the practice rounds here, just playing nine holes each day, and carry that momentum through to the first round, which I've managed to do."
Poulter is another player looking for form after an injury-plagued season, but the 38 year old looked to have found it courtesy of some lengthy practice sessions this week.
Asked what was most pleasing about his 68, Poulter said: "The overall state of my game, because it hasn't been there for a little while.
"I think the work that I put in Monday, Tuesday, Wednesday was rewarding to go out there to play well. It's the most balls I've hit in any session. The body is allowing me to hit more balls at the minute, which is a good thing. It's coming into the right time of the year."