Rory McIlroy made a stunning return to the scene of his lowest point of 2013 to take a first-round lead at the Honda Classic.
The tournament - the start of the PGA Tour's Florida Swing - has attracted most of the game's leading lights with seven of the world's top 10 in action.
It was McIlroy, the world number eight, who was the most impressive of them, shooting seven birdies in a bogey-free seven-under-par round.
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."
Henley, playing the back nine first, started superbly, picking up birdies at his first four holes and another at his sixth - the 15th - where he was close to a hole in one.
Another birdie followed at the fifth but he needed to recover from some tricky positions to avoid any blemishes on his card.
Most notably, he hit one shot out of water at the third to enable himself to save par.
Another American, Matt Every, threatened to get close to McIlroy after birdying the 14th to move five under and then having a chance to gain another stroke at the 15th.
But his birdie putt did not drop and a bogey at the 16th saw him slip back to four under and into a tie for sixth.
Donaldson had a fine day, with an eagle at the 18th and five birdies in his 65.
Luke Donald was two shots further back on three under after a 67 with Lee Westwood two under.
The poor form of world number one Tiger Woods continued as he carded a one-over-par 71.
The damage for Woods was done on his front nine with a double bogey at his second and bogeys at his fifth and eighth.
Woods said: "It certainly wasn't together today.
"I hit it good enough to shoot probably at least three or four lower than I did.
"I had so many looks where I just missed. I just need to read them a little bit better than I did today."