Jason Caron and Kevin Durkin, who are each seeking their first win on the Nationwide Tour, share second place at 4-under-par 66.
Adamonis opened his round on the first tee at Troy Burne Golf Club. He dropped his third shot within 2 feet of the cup for a birdie at No. 1, but found water off the tee at the next hole en route to a bogey.
The 31-year-old caught fire from there. Adamonis knocked his tee ball to 12 feet for birdie at the third. He came right back at the next with a 2-foot birdie putt, and made it three in a row with a 7-footer for birdie at the fifth.
Adamonis climbed to 4-under when he rolled in a birdie try from 15 feet out at the seventh. Around the turn, he drained a 30-footer for birdie at No. 10. However, he faltered to a three-putt bogey at the next.
The Rhode Island native dropped a wedge inside 8 feet for birdie at the 14th, but stumbled to a bogey at the next when he again three-putted. Adamonis capped his round with a chip-in birdie at the 16th to take the lead.
'I played well,' said Adamonis, who leads after any round for the first time in his career. 'I just took it one shot at a time. I'm surprised, I didn't think I would be in the lead.'
Caron started on the back nine and stumbled to a bogey at the par-4 12th. He picked up two birdies on his way to the front side. Around on the front nine, Caron birdied the second and eagled the 591-yard, par-5 fifth to climb into second place.
'Great start to the tournament,' Caron said. 'I am hitting it solid and not making mistakes. It's nice to have that train of thought where you know you're going to chip-in for par on No. 9.'
Durkin also started on the back nine and dug himself a deep hole right away. He double bogeyed the 10th and bogeyed the 12th. He did manage a birdie in between on No. 11, so he was 2 over par through three holes.
The 30-year-old picked up birdies at the 16th and 18th to make the turn at even-par. Durkin made it three in a row as he birdied the first and second.
Durkin continued his hot play with a birdie at the fifth, and moved into a share of second place with a birdie at the par-4 seventh.
'I started off real slow, but I got it back,' said Durkin, whose best tour finish was a tie for eighth at the 2003 Oregon Classic. 'The front side you should take it a few under and have some fun.'
Mathew Goggin and Darron Stiles each posted rounds of 3-under-par 67. They share fourth place with John Elliott, Rick Fehr, Stephen Gangluff, Troy Matteson, Mike Sposa, Charles Warren, Nick Watney and Brian Wilson.
Doug LaBelle II and Michael Long lead a group of 13 players that are one stroke further back at minus-2.