An error-free round from Matt Kuchar saw the American open up a one-shot lead at the Northern Trust Open in California.
Kuchar got off to a flying start with three successive birdies before picking up four further shots to finish with a seven-under-par 64.
That was enough to give him a narrow advantage over Sergio Garcia, who could have been in a share of the lead had he not dropped a shot at the 13th.
"It's always fun to have bogey free days, especially around this golf course," Kuchar said on pgatour.com. "I just drove it well today which is a big key around here.
"The greens are pretty tricky and pretty firm this year, so coming out of the rough, it's difficult to get a ball to stop close to the hole.
"Coming out of the fairway is a key thing to play some good golf, so we are driving it well and I played some nice golf today."
Brandt Jobe was a further shot off the pace on five-under, while Englishman David Lynn, James Hahn and Charlie Beljan are on four-under.
Lynn was the pick of the British and Irish contingent - with Lee Westwood on three under, Luke Donald and Greg Owen two under and Brian Davis one under.
The news wasn't as encouraging for Ross Fisher, who was one over, Graeme McDowell (two over), and Martin Laird (three over), while three-time major-winner Padraig Harrington had a day to forget as carded two bogeys and two doubles to finish six over.
Play ended with 18 men yet to complete their rounds because of fog and darkness.
Pre-tournament favourite Phil Mickelson carded a level par 71 in a round featuring four birdies and four bogeys.