Dustin Johnson grabbed a two-stroke lead in Friday's second round of the 77th Masters while world number one Tiger Woods opened with a par on a difficult day for scoring at Augusta National.
Johnson opened with a five-under par 67, the best round of his career at Augusta National, then caught fire on day two after bogeys on the first and third holes.
The 28-year-old American birdied the par-3 fourth, added back-to-back birdies at the ninth and 10th and followed with a birdie at the par-5 13th to reach seven-under par for the tournament.
Moments later, Australia's Marc Leishman, who had been level with Johnson for the lead, took a bogey at the fourth and fell back to five-under in second place. Leishman is trying to become the first Australian to win the Masters.
Johnson seeks his first major title. He shared second behind Darren Clarke in the 2011 British Open and was in the hunt at the 2010 PGA Championship before a two-stroke penalty for grounding his club in a bunker ended his hopes.
Still on the course at four-under were Fred Couples with five holes to play, Jim Furyk, Rickie Fowler and South African Charl Schwartzel.
Another stroke back on three-under were England's Justin Rose and Americans Brandt Snedeker and Matt Kuchar.
Chinese 14-year-old schoolboy Guan Tianlang, the youngest player in Masters history, was two-over for the day and three-over for the tournament after 16 holes and likely to be the only amateur player to make the cut.