American Boo Weekley and Zimbabwe's Brendon de Jonge registered first-round 64s to earn a one-stroke lead at the Zurich Classic of New Orleans on Thursday.
Weekley holed seven birdies and an eagle, while De Jonge had eight birdies in a bogey-free round as both players ended the opening round eight shots under the card at TPC Louisiana.
Canadian David Hearn and American Sean O'Hair are one shot off the pace heading into day two.
Weekley, who missed three consecutive cuts before finishing tied for 75th at last week's RBC Heritage, produced his best opening-round score in more than two years, which was set up by a second-hole eagle.
The three-time PGA Tour winner added three birdies before the turn, while a bogey on the ninth hole was his only blemish on Thursday.
Weekley sank three consecutive birdies starting at the 11th, and he capped his best start to a tournament since October 2012 with a final-hole birdie.
"You can't win the tournament today," he said. "There's a lot of golf left. We're all out here hitting it the same. The difference is who's hitting it the closest.
"But I saw the good today. If you don't hit it good tomorrow, you don't hit it good."
De Jonge - bidding to win his first PGA Tour event - was faultless through 18 holes.
The 34-year-old, who started on the back nine, had birdies at the 11th, 12th, 13th and 16th holes, while he added another four after the turn for a share of the lead.
Daniel Berger, Erik Compton, Brian Davis, Mark Hubbard and Greg Owen are tied for fifth at six under.
KJ Choi, Dustin Johnson, Jason Day, Ben Crane, Derek Ernst, Chris Stroud, Blayne Barber, Carlos Ortiz, Chad Campbell, Chesson Hadley, Jhonattan Vegas and Hudson Swafford are a shot further back.
Defending champion Noh Seung-Yul carded a one-over 73 to be tied for 113th.