Former British Open winner and first-round co-leader Ben Curtis shot a 2-under 68 and is tied for second place with Kevin Sutherland, who posted a 67 on Friday. The duo is knotted at 8-under-par 132.
Rose, who was one shot off the lead after round one, wasted little time in breaking into red figures on Friday. He wedged his approach to 8 feet at the first and sank the birdie try. Rose made it two in a row at the second, this time from 6 feet.
At the par-5 sixth, Rose hit a 5-wood into the greenside bunker. He blasted out to 8 feet and drained the birdie try, then tapped in a 4-footer at the seventh.
Rose parred out around the turn then hit a sand-wedge to 10 feet at the 12th and rolled in the birdie try. One hole later, Rose hit his 'best shot of the day' when his 5-wood second shot at the par-5 hole nearly landed in the cup. It rolled 15 feet past the cup and he two-putted for another birdie.
Rose polished off three birdies in a row at No. 14. He hit a pitching-wedge to 5 feet and holed the birdie putt to reach 12 under par for the championship.
He parred his last four holes and now Rose has the 36-hole lead on the PGA Tour for the third time in his career.
'I was never in a situation where I couldn't reach the green, so I felt that was what I did well today,' said Rose. 'I think I'm probably more pleased about the fact that I've kept a bogey off my card, than 12 birdies.'
Rose hit the golf world in a big way when he tied for fourth in the 1998 British Open as an amateur. He went through a horrible stretch of missed cuts when he turned professional shortly after that British Open, but recently his game seemed to have come around.
He held the 36-hole lead at last year's Masters before tying for 22nd. Rose also had a piece of first midway through the Memorial later in 2004, but came in fourth.
Rose has four wins outside the United States, but has yet to visit the winner's circle on the PGA Tour. His best finish is a third at the 2003 Deutsche Bank Championship, and in a season where he has yet to post a top-10, this becomes a very important weekend.
'Obviously tomorrow I'm not going to think about winning; it's the halfway point,' said Rose. 'I'm not uncharted, it feels like I haven't been there in a while, and certainly to lead by four at the halfway stage is a little different.'
Curtis, who won the British Open in 2003, flew out of the gate on Friday. He started on the back nine and hit a 5-iron to 20 feet to set up birdie at the 10th. He collected his second birdie in four holes with a two-putt from 40 feet at the par-5 13th, then drove it to the fringe at the reachable 15th and lagged his eagle try to a foot.
Things fell apart quickly for Curtis. He found water at the 16th and did well to save bogey, his first of the tournament. That bogey knocked Curtis down to 8 under par for the championship.
He parred his next 11 holes to grab his share of second place.
'I think any time you can shoot under par, it doesn't matter if it's 71 right now for me,' said Curtis. 'It just feels good to go out there and shoot a good number.'
Sutherland mixed six birdies and three bogeys in his round on Friday.
Michael Putnam, who is making his professional debut this week, shot a second-round, 1-under 69 and is tied for sixth place. J.J. Henry (67), Tjaart van der Walt (66), Robert Allenby (66) and Tim Petrovic (67) joined Putnam at minus-6.
J.L. Lewis, who shared the lead with Curtis on Thursday, struggled to a 4-over 74 and is part of a group tied for 37th place at 2-under-par 138.
Jason Gore, who played in the final group on Sunday at the U.S. Open, is playing his first PGA Tour event since earning a 'battlefield promotion' from the Nationwide Tour.
After a 4-over 74 on Thursday, he rebounded with a 5-under 65 and is tied for 51st at minus-1.
The 36-hole cut came in at even-par 140 and American Presidents Cupper Fred Funk (142) and PGA Championship runner-up Steve Elkington (144) will miss the weekend.