Dustin Johnson fired a seven-under 64 to climb into a share of the Pebble Beach Pro-Am lead after the second round.
The world number one made eight birdies on the Monterey Peninsula Country Club course to move into 12 under in Pebble Beach, California, on Friday.
A two-time winner of the PGA Tour event, Johnson started on the back nine and holed five birdies, before three in four helped him into the lead.
Johnson has made a fine start to this year, winning the Tournament of Champions before a top-10 finish at the Abu Dhabi HSBC Championship.
Joining him atop the leaderboard is fellow American Beau Hossler, who carded a five-under 67 on the Spyglass Hill Golf Course.
Hossler backed up his opening-round 65 with a bogey-free Friday.
Troy Merritt (67 on Spyglass Hill) and Julian Suri (67 on Monterey Peninsula) are two shots back in a tie for third.
A further shot adrift are the likes of four-time champion Phil Mickelson, Spaniard Jon Rahm and Australian Jason Day.
Rahm, the in-form world number two, carded a second straight 67 to be in the six-man group at nine under.
Day and Mickelson fired six-under 65s on Monterey Peninsula, with Aaron Wise, Kevin Streelman and Steve Stricker joining the group in a tie for fifth.
Defending champion Jordan Spieth managed to get going, shooting a five-under 66 on Monterey Peninsula to be tied for 23rd.
Making his first PGA Tour appearance of the season, Rory McIlroy struggled on the same course.
The Northern Irish four-time major champion carded a 74 to slip back to one under as he endured a forgettable few moments on the par-four fifth hole.
McIlroy had an eagle putt at the hole, but left with a double bogey after an implosion, before two more bogeys followed to finish his round.
|Sordet leads Nordea Masters, Olesen overcomes flight woes|
|Mourinho visits Istanbul Basaksehir before Burnley game|
|Iniesta hails ´worldwide sports legend´ Alonso|
|Onus on Ozil to rise above criticism, says ex-Arsenal star Wright|
|Lahm to head Euro 2024 if Germany wins bid|
|Tennis Australia ´extremely disappointed´ with Davis Cup revamp|
|Snedeker shoots 59 at Wyndham, after bogeying his first hole!|
|Lukaku hints at Belgium retirement after Euro 2020|
|Pellegrini rules out West Ham approach for Toure|
|Association of Spanish Footballers fumes at LaLiga´s US agreement|
|Seibold and Bennett hit out at media speculation|
|Cipriani ´truly sorry´ after pleading guilty to common assault|
|Man City´s Roberts makes Girona loan move|
|Davis Cup revamp passed by two-thirds majority vote|
|Pochettino ready to tackle Man City after Wembley NFL|
|Emery ends Arsenal goalkeeper debate with Cech assurance|
|Shastri: India happy to face Stokes in Nottingham|
|Etzebeth returns for Springboks, Pumas include Figallo|
|Two Serie A matches postponed after Genoa bridge collapse|
|Barrett tight-lipped over Manly future due to ´legal reasons´|
|N´Zonzi is better than Malcom - Monchi takes aim at Barca star|
|Sainz to replace Alonso at McLaren|
|Bayliss encourages Stokes to make public apology|
|Oates hat-trick boosts Broncos´ play-off ambitions|
|Emery needs four transfer windows to impact Arsenal – Wright|
|Spain´s LaLiga plans to play regular-season game in U.S.|
|´Dream come true´ for Robertson to earn Bledisloe Cup start|
|LaLiga match set for USA following groundbreaking Relevent deal|
|FIFA rankings: France number one, Croatia and England soar, Germany and Argentina plummet|
|Hansen hails ´big leader´ Whitelock ahead of 100th cap|
|Cipriani pleads guilty to common assault and resisting arrest|
|PSG snap up Kehrer from Schalke|
|Maitland-Niles facing two months out with broken leg|
|Walker backs City squad strength to overcome De Bruyne blow|
|Thomas & Froome skip Vuelta, named in Tour of Britain squad|
|Thurston rules out retirement U-turn|
|Pumas look to build on Jaguares progress in Rugby Championship|
|Super Cup glory will make Atletico strong - Simeone|
|Rugby Championship 2018: True status of Erasmus´ Springboks rebuild to be discovered|
|LaLiga 2018-19: Coutinho ready to be Barca´s next Brazilian superstar|
|Serie A 2018-19: Can Napoli, Roma, Inter or AC Milan overhaul Juventus?|
|Braves survive skirmish, loss of Acuna to top Marlins|
|Robertson handed surprise start, Hodge gets nod for Bledisloe opener|
|MLS Review: Wayne´s World as Rooney inspires DC United, LAFC win|
|Djokovic and Dimitrov survive but Zverev loses in Cincinnati|
|Rain halts Halep as Muguruza´s defence ends and Wozniacki retires|
|Ozil´s racism claims nonsense, says Kroos|
|Malcom lost for words after Camp Nou bow alongside Messi|
|Injured Fowler withdraws from play-off opening Northern Trust|
|Marcelo happy with Madrid squad amid transfer talk|
|Foles isn´t worried about Brady´s handshake snub|
|Eli Manning on Jalen Ramsey´s comments: ´Who?´|
|Cerezo: Atletico´s objective is to reach Champions League final|
|Judge´s recovery taking longer than expected|
|Ronaldo in the past as Casemiro backs Lopetegui after Madrid loss|
|With our ´cojones´ Atletico can beat anyone – Costa revels in Super Cup glory|
|Super Cup loss doesn´t change Real Madrid transfer policy, says Lopetegui|
|Griezmann: Super Cup triumph justifies staying at Atletico|
|Valverde defends Suarez performances|
|Simeone´s eclipses Aragones as Atletico´s top coach with seventh title|
|Rockets GM: LeBron James is ´the greatest ever´|
|Salihamidzic, Kovac not standing in way of Rudy exit|
|Jaguars DB Ramsey calls Bills QB Allen ´trash´|
|Real Madrid 2 Atletico Madrid 4 (after extra time): Saul stunner seals Super Cup glory|
|Ex-India Test captain Wadekar dies aged 77|
|Gundogan ready to step up in absence of injured De Bruyne|
|Djokovic overcomes illness to see off Mannarino|
|Diego Costa nets fastest UEFA Super Cup goal ever|
|Everton feared missing out on Mina after World Cup strike|
|Barcelona 3 Boca Juniors 0: Messi, Malcom net as Barca win Joan Gamper Trophy|