American Robert Garrigus shot a six-under 64 on Saturday to take a one-shot lead after three rounds of the $US5.2 million ($A5.02 million) USPGA Tour's Canadian Open.
Garrigus, who is chasing his second Tour win, finished 54 holes at 16-under-par 194 at the Hamilton Golf and Country Club course.
His total is one shot better than the tournament's 54-hole scoring record set initially by Arnold Palmer in 1955.
Garrigus said his game plan for the fourth round is simple: "Foot to the floor, as much as possible."
Second round co-leader Scott Piercy shot 67 for the second consecutive day and is alone in third at 14-under-par 196, while William McGirt posted a 66 for the second straight day to get to second at minus-15.
Scott Stallings and Chris Kirk both fired seven-under 63s Saturday. They share fourth place at minus-12 with Bo Van Pelt, who fired a 67.
Two years ago in Memphis, Garrigus stumbled to the finish losing a three-shot lead on the final hole but he doesn't expect to have a collapse on Sunday.
"A lot of guys haven't been able to hold leads this year," said Garrigus.
He two-putted for par on his final six holes Saturday.
"It was good to great," Garrigus said of his putting. "I made a couple of long ones, which you need to make. When you make long putts and you're in contention, it puts you up there. I felt like I putted well today. I didn't have a three-putt and didn't have a bogey."
Piercy remained in the hunt with a round that included six birdies and three bogeys.
Kirk recorded seven birdies in an eight hole stretch beginning at the par-four third hole.
"I was just trying to keep my head down and keep going," he said. "When you have those days where everything is going in the hole, you make as many as you can."