Twice winner Tiger Woods was on the brink of a record-breaking victory at the PGA Championship after stretching his lead to five strokes with three holes remaining in Sunday's final round.
In pursuit of his 12th career major, the world number one was five under for the day and 19 under for the tournament after delivering an ice-cool display of bogey-free golf in bright sunshine at Medinah Country Club.
Tied for the overnight lead with playing partner Luke Donald of Britain, Woods immediately broke clear by rolling in a 10-foot birdie putt at the par-four first.
He picked up his second shot after reaching the green in two at the 537-yard fifth, coolly sank a 35-footer at the par-four sixth and holed a downhill 30-footer to birdie the par-three eighth, his ball threatening to miss on the high side before it tantalisingly dropped into the cup.
After reaching the turn four strokes ahead of the chasing pack at 18 under, Woods picked up his fifth shot of the day at the par-four 11th after hitting a brilliant approach shot from the right rough to within 10 feet of the flag.
Oozing confidence on another day of low-scoring, he is on pace to break the PGA Championship's 72-hole scoring record which he holds jointly with fellow American Bob May.
The pair completed four rounds in the 2000 tournament at Valhalla in 18-under 270 before Woods won the title for a second time in a playoff.
American Shaun Micheel, winner of the 2003 PGA Championship at Oak Hill, was alone in second place after 16 holes with Canadian left-hander Mike Weir, the 2003 Masters champion, a stroke behind in third at 13 under, after 15 holes.
Englishman Donald, bidding to become the PGA Championship's first European-born winner in 76 years, was tied for fourth at 12 under, level with Australia's Adam Scott and Spaniard Sergio Garcia.
Donald, who has a home in nearby Chicago, bogeyed the fourth and 10th and was two over for the round after 15 holes.
Scott surged up the leaderboard with a closing 67 to finish at 12-under 276 while Garcia, runner-up to Woods in the 1999 PGA Championship at Medinah, was two under for the day after 16 holes.
Woods, who won last month's British Open at Hoylake by two shots, has never lost when leading or holding a share of the lead going into the final round of the game's biggest events.
He fired a course-record tying 65 in Saturday's third round and is on track to move past fellow American Walter Hagen in the all-time major standings.
Hagen and Woods lie joint second with 11 victories with only Jack Nicklaus, on 18, ahead of them.