Jay Haas and Duffy Waldorf each carded a 5- under 66 on Thursday to share the lead after one round of the Senior PGA Championship.
Kiyoshi Murota and PGA Club Professional Sonny Skinner shared third place at 4-under 67 at the Champions Tour's first major of the season.
"Just to be here is very special," said Skinner. "I'm very thankful the PGA of America has the eligibility requirement that they do that allows as many club pros to get into our tournament as they do."
Peter Senior and Chien-Soon Lu sit in a tie for fifth at Bellerive Country Club at 3-under, while 39-time PGA Tour winner Tom Watson is among a large group of players tied for seventh place at minus-2.
Defending champion Roger Chapman finished with a 1-over 72 to sit in a tie for 46th place.
Haas opened his round with five straight pars before picking up a pair of birdies at the sixth and eighth to hit the turn at 2-under.
The St. Louis native added back-to-back birdies at the 11th and 12th, and later rolled in another birdie at the 15th to reach 5-under.
He completed his bogey-free round with three straight pars to remain there.
"I'm certainly very excited about shooting 5-under here," said Haas. "It's probably my lowest score ever at Bellerive, no matter what age I was. I didn't expect it going out. I wasn't very sharp today, but managed to keep my misses in the correct spots and I took advantage of a few good iron shots and just kind of kept it between the ditches, I guess you would say. But very, very pleased with that."
Waldorf teed off with one of the last groups of the day and started on the back nine, picking up birdies at the 12th, 14th and 16th to make the turn at 3-under.
He poured in another birdie at the fourth to move within a stroke of the lead, but a bogey at the fifth dropped him two strokes behind Haas.
Waldorf bounced back with birdies at the seventh and eighth to meet Haas at 5- under and closed with a par at the ninth.
"All in all hit the ball really well tee to green. I really liked my iron play," Waldorf said. "I didn't make a ton of putts, but I had some real nice up and downs which really saved the round."
Murota quickly picked up a couple of shots with birdies at the second and fourth, but tripped to a five at the par-3 sixth to fall back to even par.
However, he quickly recovered with consecutive birdies at the seventh and eighth to get back to 2-under.
After recording another birdie at the 12th, he parred his next five holes before birdieing the last to finish at 4-under.
Skinner started on the back nine and bogeyed the 11th and 16th around a birdie at the 15th to sit at 1-over, but answered with a run of five birdies over his next six holes to move to 4-under.
He closed with five straight pars to stay a shot off the pace.
NOTES: Steve Elkington withdrew prior to the start of the first round due to a migraine ... Skinner was the low PGA Club Professional at the 2011 Senior PGA Championship. He is the club pro at River Pointe Golf Club in Albany, GA ... Haas' 66 was his lowest round in a Senior PGA Championship event.