American golfer Bill Haas grabbed a one-stroke clubhouse lead over defending champion Adam Scott and 2010 British Open winner Louis Oosthuizen of South Africa in Thursday's first round of the 78th Masters.
Haas answered a bogey at 17 with a closing bogey to open on four-under par 68 after 18 holes at Augusta National.
Scott, who last year became the first Australian winner in Masters history, was on three-under with one hole to play while Oosthuizen was level with seven holes remaining.
Six players were in the clubhouse sharing fourth on 70, including South Korean K.J. Choi, Sweden's Jonas Blixt and Americans Kevin Stadler, Jimmy Walker, Gary Woodland and Brandt Snedeker.
Rory McIlroy was on two-under after 16 holes.