Kirk Triplett hit the best opening round in US Senior Open history to lead by a stroke at the end of the first day at Salem Country Club.
Triplett shot an eight-under 62 in Massachusetts on Thursday to equal the same score as Loren Roberts made in 2006 for the joint-best round of all time in the tournament.
The 55-year-old could have broken the record, but missed a birdie opportunity on the final hole to maintain a lead over compatriot Olin Brown on six under, while Doug Garwood finished a shot further behind after a round of 64.
Elsewhere, Englishman Barry Lane enjoyed a good start as he hit a five under to tie for fourth, the only American inside the top 10, while Miguel Angel Jimenez hit a round of 67 to put himself in contention ahead of the rest of the weekend, the same score as Bernhard Langer.
1992 Masters Champion Fred Couples went round in two under, while Tom Watson finds himself a stroke further back. And Colin Montgomerie and Nick Faldo, playing his first US Senior Open, finished on one over and three over respectively.