Donald has played 36 holes since his last bogey at Medinah
US unless stated
-14 T Woods, L Donald (Eng)
-12 M Weir (Can)
-11 G Ogilvy (Aus)
-10 S Garcia (Spa), S Micheel
-9 KJ Choi (Kor)
-8 Chris DiMarco, Phil Mickelson, Ian Poulter (Eng), Tim Herron
England's Luke Donald and American Tiger Woods will go into the final round of the USPGA on Sunday tied on 14 under, two shots clear of the field.
Donald carded a six-under 66 on Saturday to match the target set by Woods, who had earlier equalled the course record with a seven-under 65.
Canada's Mike Weir is in third place on 12 under after he too posted a 65.
US Open champion Geoff Ogilvy, who played with Woods in the first two rounds, is a shot further back.
With the course softened by Friday's rain, conditions at Medinah were perfect for low numbers, and the players obliged.
Spain's Sergio Garcia and American Shaun Micheel, the 2003 USPGA champion, shot 67s to get to 10 under, while Korea's KJ Choi fired a 67 to reach nine under.
Saving par on the 1st was key - after birdies on the next two I was off and running
American Ryder Cup hopeful Chris DiMarco matched their scores to reach eight under, the same total as world number two Phil Mickelson and England's Ian Poulter, who both signed for 68s.
American Tim Herron, who played with Donald, later joined them in a tie for eighth, although he could only manage a level-par 72.
The 31-year-old Poulter posted five birdies on Saturday but admitted he would need plenty more on Sunday if he is to win the first major of his career and Europe's first since 1999.
He also said that with the greens this receptive it was still possible for a player to go "really low" and come through the field. They could, of course, but with Woods enjoying a share of the lead it is unlikely.
The 30-year-old superstar has won all 11 of his major titles when either leading or sharing the lead after the third round.
Woods holed a huge putt at the 1st for par and never looked back
If that is not daunting enough for the 28-year-old Donald and the chasing pack, Woods is looking for his second straight major victory after his triumph at Hoylake last month and third successive tournament win.
And just for good measure he has shot in the 60s in 13 of his last 14 rounds - and he won this title, which no European has won since 1930, when it was last held at Medinah in 1999.
That was the year Skip Kendall shot the 65 that Woods and Weir equalled on Saturday.
But Donald will not lack for encouragement - he has been getting huge support from the galleries all week thanks to his links with the area - and he has also demonstrated he is capable of staying with Woods.
Donald, who lives in nearby Chicago and was a star player on the golf team of Northwestern University in Evanston, Illinois, was two shots clear of the field on 13 under after a great front nine.
"I saw a little bit of the early golf and knew I needed a fast start," said Donald. "Saving par on the 1st was key - you never want to bogey the first - and after birdies on the next two I was off and running."
But as the birdie putts started to stay up for the Hemel Hempstead-born Donald, Woods was moving through the gears as only he can.
Three straight birdies from the 13th put the American into the lead for the first time - usually an ominous moment in any tournament - but he then bogeyed the 16th to slip back to 13 under.
Woods repaired the damage with a birdie at 17 before parring the last for the clubhouse lead.
Donald, meanwhile, had saved par superbly at 16 with a brave up-and-down from a greenside bunker and birdied the short 17th to also reach 14 under.
Weir, the 2003 Masters champion, was in stunning form on Saturday
Earlier on Saturday, rising American star Ryan Moore flagged up what was possible on "moving day" by firing a five-under 67.
And American Joey Sindelar claimed only the third albatross in USPGA history by holing his second from 241 yards at the par-five 5th.
The scoring was so spectacular, particularly on the front nine, that at one point there were 10 players tied for the lead.
It is ironic then that perhaps the biggest play of the day was the remarkable par that Woods made at the 1st.
Seve Ballesteros at his best would have been proud of such escapology, and when the tournament is over it could be settled not by the birdies the winner has made but by the bogeys he didn't.
But then Donald already knows that.