Rory McIlroy made a perfect start in his bid to regain the Honda Classic at Palm Beach Gardens.
Twelve months ago the former World Number One was unable to defend the title he won in 2012 after pulling out with toothache.
But a year on the Northern Irishman shot a superb 63 to claim a one stroke advantage after day one.
The World Number Eight shot seven birdies in a bogey-free seven under par round.
American Russell Henley was second at six under with Rory Sabbatini, William McGirt and Welshman Jamie Donaldson in a three-way tie for third at five under.
The highlights for McIlroy included a long putt for birdie at the par four 11th and a fine bunker shot at the last to set up another birdie chance.
McIlroy said: "I played really solid. I think the key around here this week is hitting fairways and greens.
"It is ball-striker's golf course. If you can keep the ball in play and give yourself birdie chances, that is the name of the game here."