Germany's Martin Kaymer produced a birdie burst on the back nine to take a three-shot lead after day one of the US Open.
Kaymer, winner of the prestigious Players Championship last month, looked as if he would be part of a bunched leaderboard at Pinehurst No 2 in North Carolina after going to the turn in a steady one-under 34.
But after a birdie at 10 tied him with early clubhouse leaders Graeme McDowell and Kevin Na, the 29-year-old separated himself from the field.
Birdies at 14, 16 and 17 lifted him to five-under and he calmly rolled in a nine-foot par putt at the last to complete a back-nine 31 and post a superb 65. That beat the previous lowest score in a US Open at Pinehurst of 66 by Peter Hedlbom in 2005.
Having started in the afternoon wave on Thursday, 2010 US PGA winner Kaymer will now have the chance to kick further clear when he tees off early on Friday.
Kaymer, whose putt on the 18th green at Medinah in 2012 kept the Ryder Cup in European hands, said: "It was very nice. I didn't make many mistakes. And finally I could make some putts on 15, 16 and 17.
"If you shoot anything under par or level par on that golf course, it's good.
"I watched some golf this morning and I was very surprised how playable it was because yesterday (in practice) I played in the morning and it was very firm so they must have put a lot of water on the greens last night."
He admits. though, that the course is only going to get tougher. "Usually, it only gets more difficult and more firmer and faster," said Kaymer.
McDowell and Na had shot their two-under 68s in the morning and they were later joined on two-under by Zimbabwe's Brendon de Jonge and American qualifier Fran Quinn.
Northern Ireland's McDowell, the 2010 US Open champion at Pebble Beach and runner-up at Olympic Club in 2012, had just one bogey and holed from 10 feet for eagle on the fifth after a superb three-wood approach from 248 yards.
He admitted: "It wasn't my best ball-striking display this morning, but you don't have to strike it amazing around here, you just have to position the ball correctly at all times."
Sweden's Henrik Stenson, who can become world No 1 by claiming his first major title on Sunday, is among a big group on one under after being one of the early starters who made the most of more receptive greens than had been expected. His 69 was matched by Ryder Cup stars Brandt Snedeker, Matt Kuchar, Dustin Johnson and Keegan Bradley, along with American youngster Jordan Spieth and Italy's Francesco Molinari.
Six-time runner-up Phil Mickelson, looking to become only the sixth player to win all four major titles, is another shot back on level par alongside England's Ian Poulter and Ryder Cup hopeful Joost Luiten.
Sheffield amateur Matt Fitzpatrick briefly held a share of the lead after starting with two birdies in his first three holes, the 19-year-old eventually signing for a 71 despite a penalty shot on his penultimate hole when his ball moved as he prepared to play his third shot.
That was still one better than playing partner and defending champion Justin Rose, who at least recovered from being four over par at the turn.
Former champion Rory McIlroy was alongside Fitzpatrick on one over after struggling to get the pace of the greens.
While 2011 US Open winner McIlroy will remain hopeful of adding a third major title, Lee Westwood and Luke Donald have a mountain to climb if they want to win their first.
Morning starter Westwood had seven bogeys in a five-over 75 while Donald had eight bogeys on his card and signed for a seven-over 77.
World No 1 Scott once again failed to produce his best in the year's second major - he's never been better than 15th - and posted a three-over 73.