American Harris English fired a round of 67 to stride out to a two-stroke lead at the halfway mark of the Sentry Tournament of Champions in Hawaii on Friday.
Teeing off with a share of the lead with compatriot Justin Thomas after both shot first-round 65s, English turned in a faultless display, collecting three birdies on both nines to end the day at 14-under-par.
Thomas began well with a flawless front nine of four under par, but could not improve coming home - with a bogey cancelled out by a birdie on the last - to end the round on 12 under.
He is in a share of second place with three fellow Americans - Daniel Berger and Collin Morikawa, who shot 65s - and Ryan Palmer, who has carded two rounds of 67.
Xander Schauffele and Patrick Reed are in a group of four sharing sixth place a stroke further back, while Dustin Johnson, Bryson DeChambeau and Spain's Jon Rahm are lurking in a group a further shot away at 10 under.
Scotland's Martin Laird, the only Briton in the 42-person field, shot a second straight 69 - with four birdies and no bogeys - to be six off the pace at eight under.
