Rob Oppenheim, who played on the Canadian Tour this year, shot a 7-under 65 at Del Monte Golf Course to take the first-round lead.
Oppenheim had seven birdies in a bogey-free round on the shortest of the three courses used in the tournament that includes players from the four major tours, former PGA Tour pros, club professionals and amateurs.
The 14 LPGA and five Champions Tour participants receive distance advantages on most tee shots.
Thorpe is tied for second with PGA Tour rookie Dean Wilson.
Scott Miller, one of four sons of former U.S Open winner Johnny Miller competing in the tournament, shot a 68 at Spyglass Hill, and was tied with Charles Warren, defending titleholder Mark Brooks and Steve Flesch.
John Daly, a late addition, trailed Oppenheim by four shots after shooting a 69 at Pebble Beach. Kelli Kuehne, who leads the LPGA entrants, is also in the group at 69.
The tournament concludes Sunday at Pebble Beach, with the top 40 pros and 10 top amateur teams competing in the final round.
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