Jordan Spieth threatened to turn the year's first major into a runaway as he fired a six-under-par 66 for a five-shot lead and a Masters record for lowest 36-hole total at Augusta National.
Playing with a steely focus and pinpoint precision, the 21-year-old Spieth reached the halfway mark on 14-under-par 130 to surpass the 131 posted by Raymond Floyd on his way to winning the 1976 Masters.
Spieth, with 15 birdies and one bogey in his two rounds, also equalled the lowest 36-hole total for any major championship.
Spieth led by five over compatriot Charley Hoffman, who registered five birdies but bogeyed the last for a 68 and nine-under 135 on a hot, humid day amid the Georgia pines.
"It's cool. Any time you can set a record here is pretty awesome," said Spieth. "I'm very excited about today and the way I struck the ball."
Dustin Johnson set another Masters mark as he flew up the leaderboard with a record three eagles on the par-fives to record a 67 for seven-under 137.
Former U.S. Open winner Justin Rose (70) and fellow Englishman Paul Casey (68) were also on 137.
Tiger Woods climbed up the leaderboard as the four-time champion shot a 69 to stand two-under and tied for 19th. He had shared 41st place after an opening 73 in his return to competition following a two-month absence.
World number one Rory McIlroy, who needs a Masters victory to complete a career grand slam, looked as though he might miss the cut when he went out in four-over 40 to stand three-over.
But the 25-year-old Northern Irishman posted 31 on the back nine for 71 to join Woods on 142.