Phil Mickelson, the 1993 winner of the event, fired a seven-under 65 and shares the leadership with Joel Edwards, Dan Pohl, Chris DiMarco and Jerry Haas. Craig Stadler, the defending champion, is in a group of 10 golfers two strokes back on 67. Ireland's David Feherty started well with a fine 69.
Haas had seven birdies and Pohl five birdies plus an eagle at the par- five 18th. Edwards' iron play was among the best in the field on Thursday, with all six of his birdie putts set up by approach shots within five feet of the cup. Peter Jacobsen, the winner of the Pebble Beach National Pro-Am last week, shot a 68.
Mickleson said: "I've played so well here in the past. I played well again today. I made some good six to eight-footers. The scores are going to be low because the fairways and greens are immaculate."
BUICK INVITATIONAL OF CALIFORNIA (La Jolla) Leading first-round scores (US unless stated): 65 P Mickelson, J Edwards, D Pohl, C DiMarco, J Haas. 66 P Stewart, D Ogrin, B Faxon, B Burns, B Chamblee. 67 H Sutton, L Nelson, C Stadler, J Hayes, K Gibson, M Brisky, S Verplank, D Paulson, S Stricker, L Rinker. 69 D Feherty (GB). 71 S Rintoul (Aus), N Faldo (GB).