This isn't Michael Thompson's first USGA event at The Olympic Club, and he used his prior knowledge of the course to shoot a four-under 66 and take the early lead at the 112th U.S. Open.

Five years ago, Thompson lost to Colt Knost in the final at U.S. Amateur Championship. The USGA paired the two for the opening two rounds after Knost got into the field as an alternate.

"I thought it was a great opportunity for us to go out and have a little rematch. It was a lot of fun. Colt is a great guy, and a great competitor," Thompson said in a televised interview. "We both have a lot of good memories from this place. It's just exciting to be back here at The Olympic Club.

Three-time champion Tiger Woods and former PGA Champion David Toms both carded one-under 69s and were tied for second. Both players started on the ninth tee. The way the Lake Course at The Olympic Club is set up, it was easier for players to start on the first and ninth, instead of the normal first and 10th.

Woods' playing partners both struggled badly. Phil Mickelson and Bubba Watson each had a lone birdie in their rounds.

Mickelson started by losing his opening tee shot on the ninth. He never recovered from the opening bogey as he went on to shoot a 76, which matched his worst first-round score at U.S. Open. He also shot 76 in the opening round in 1996 at Oakland Hills.

"I didn't play very well, obviously. You could see that," Mickelson said. "I fought hard there for a while trying to keep it a few over. Three-putting No. 4 really hurt because I probably tried to get a little aggressive, I felt like I needed one birdie there and got a little aggressive and ended up three- putting. But it was a tough day when you play it the way I did."

Watson struggled to an eight-over 78. That matched his worst round in a major, as he closed with 78 at the 2011 Masters.

"I was a little off here and there. Just couldn't get anything going. Never got any rhythm, just everything was just a little off," Watson stated. "It's disappointing starting off like this, doesn't matter what tournament."

Amateur Beau Hossler posted an even-par 70 and was two off the pace with Robert Karlsson, Jae-bum Park, Jason Bohn and Alistair Presnell.

Branden Grace, a three-time winner on the European Tour this year, managed a one-over 71. U.S. Ryder Cup captain Davis Love III stands alongside 2011 Masters winner Charl Schwartzel and reigning PGA Champion Keegan Bradley at plus-three.

Andy Zhang, the youngest-ever U.S. Open participant, birdied his final hole to break 80. The 14-year-old amateur got into the field as an alternate when Paul Casey withdrew due to an injury.

Zhang started triple-bogey, double-bogey, but played the rest of the round in four-over par.

Thompson started with a bogey at the first after missing the green, but he rebounded with a birdie on the par-three third as he holed out from a greenside sand trap.

He went on to drop shots at the fifth and sixth, but it was all birdies and pars from there.

The 27-year-old moved back to even-par as he birdied the drivable par-four seventh and the par-four ninth.

Thompson continued his climb up the leaderboard with back-to-back birdies at 11 and 12. He connected on his third birdie in four holes at the 14th. Thompson closed with a birdie on the 18th to head into the clubhouse with a three-stroke lead.

"I'm not going to lie, I was a little nervous over that putt," Thompson said on TV about his putt on 18. "It was a good stroke and it barely went over the edge."

Thompson is playing in just his third major championship, and broke par for the first time in his second major championship rounds. It surely helped that he needed just 22 putts in his first round.

He played in the Masters and U.S. Open in 2008 thanks to his runner-up finish at the '07 Amateur. His best round was a closing one-over 72 that helped him tie for 29th at the U.S. Open. He also carded a one-over round at Augusta, but that was a 73. He went on to miss the cut at plus-seven by four strokes.

Woods tripped to a bogey on 14, but rebounded with a birdie on the long par- five 17th.

On the front side, he notched back-to-back birdies at four and five to move to minus-two. However, he bogeyed the sixth to fall three back.

"I played well today," Woods stated. "I felt like I had control of my game all day and just stuck to my game plan and executed my game plan."

Toms opened with a birdie on his first hole, but gave that back with a bogey on the 11th. After five straight pars, Toms birdied the 17th.

The 2001 PGA Champion parred four straight from the 18th. Toms got to minus- two as he birdied the fourth. He stumbled to a bogey on the sixth before parring his final two holes.