US Ryder Cup captain Davis Love tied the course record with a 64 to lead the Honda Classic by two shots from a group including Rory McIlroy and Justin Rose.
Love, 47, fired a hole-in-one at the fifth at PGA National as McIlroy, 22, made a good start in his chase to be world number one.
The Northern Irishman needs to win to overtake the absent Luke Donald.
Lee Westwood carded a level-par 70 and partner Tiger Woods hit 71 as Ian Poulter pulled out with pneumonia.
Veteran Love insists he will play against Europe in Chicago in September if he qualifies and capitalised on soft conditions following Wednesday's rain in Florida.
McIlroy missed the chance to rise to the top of the world for the first time when he lost to Hunter Mahan in the WGC Match Play final on Sunday.
But he made a promising start from the 10th tee in Palm Beach Gardens on Thursday, grabbing his first birdie after a 165-yard approach to five feet on the 14th.
He sunk a 12-foot putt on the short 17th for another birdie and made four on the 556-yard 18th for an opening 32.
Further birdies came on the second and seventh, with his only dropped shot coming on the eighth when he three-putted from more than 50 feet.
McIlroy said: "It's a solid opening round. I felt like the course was very scoreable this morning.
"I only made one mistake on the eighth green with a three-putt.
"Apart from that I was very happy with how the day went. I feel like I've got a few targets in my head and I'm sort of striving to get to those.
"Obviously with all of the talk of number one it would be great to get to that position at some point.
"I feel like I'm playing good enough to challenge for it at least, but I'm working towards trying to peak my game from April through to August for the four majors and for the big tournaments.
"I want to give myself the best possible chance going into those tournaments. I feel like my work ethic is probably increased a little bit this year as well.
"It comes down to hard work and just wanting it a little bit more."
Woods, who was playing the Honda Classic for the first time as a pro, was out in a stiffer breeze in the afternoon but twice lost momentum with sloppy bogeys and failed to convert a routine up-and-down on the par-five 18th.
"I didn't get a whole lot out of my round,'' said Woods, who missed only three greens but took 34 putts. "I hit the ball a lot better than I scored, and I certainly putted well, and I didn't hardly get anything out of the round. Hopefully, Friday it will be better.''
World number three Westwood swapped a double bogey at the sixth and a bogey at the 17th with three birdies.
Fellow Englishman Rose, who won the last of his three PGA Tour titles in September 2011, has slipped to 23rd in the world but came back from a double bogey on his second hole with an eagle at the next and then made three straight birdies from the fifth before a final birdie on 16.
"I guess the key was there were not any emotions to the double. It was one poor swing," he said.
"I've been losing a couple of tee shots to the right and that's what happened there, but I didn't let it affect me."
Poulter was due to play with Westwood and Woods but told his Twitter followers that he was feeling feverish just hours before the start.
After withdrawing he tweeted: "Sorry guys never been so disappointed pulling out of a tournament. Never felt so rough. Just been for a chest X-ray - got pneumonia guys. Rest time for me."