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.
|I´ll prove people wrong - Bolt completes first Mariners training session|
|Former champ Kvitova tops Radwanska, Pliskova ousted|
|Sad if it´s Filipe Luis´ last game for Atletico - Oblak|
|White Sox manager Rick Renteria hospitalised before game|
|Carragher: Van Dijk can become Liverpool legend|
|No timetable for Sale return from shoulder injury|
|This is a partnership - Rodgers on contract negotiations with Packers|
|Eagles QB Wentz unsure he´ll be cleared to play opener|
|Balotelli staying at Nice|
|It wasn´t a penalty, says Hodgson as Palace boss fumes at refereeing decisions|
|Salah can play much better - Klopp demands more from Liverpool star|
|Gasly to Red Bull: Vettel, Verstappen and the drivers who took their Toro Rosso chance|
|Klopp in the dark on Karius future amid links to Besiktas|
|Simeone pleased with draw after rigours of Super Cup|
|Captain Reus saves Dortmund in DFB-Pokal|
|I couldn´t care less - Klopp rejects title challenge talk|
|Ailing Bairstow keen to aid England´s unlikely victory bid at Trent Bridge|
|Redskins secure Peterson signing|
|Manchester City goalkeeper Bravo suffers ruptured Achilles|
|Crystal Palace 0 Liverpool 2: Milner and Mane secure victory at Selhurst Park|
|Whyte takes aim at ´coward´ Fury ahead of Wilder showdown|
|Jets delighted with Darnold, open to trading Bridgewater|
|Gasly to replace Ricciardo at Red Bull|
|Valencia 1 Atletico Madrid 1: Rodrigo strikes to deny Simeone´s side|
|Injured Halep withdraws from Connecticut Open|
|Cipriani fined £2,000 by Gloucester|
|Mourinho will be sacked before Christmas, says Sharpe|
|England face record chase after Kohli smashes India to huge lead|
|Ozil captaining Arsenal a miracle - Hoeness|
|Japan players apologise for ´thoughtless, careless´ actions at Asian Games|
|Henry wants Bordeaux job, Wenger confirms|
|Pogba too inconsistent and not a leader, claims Scholes|
|PCB chairman Sethi resigns in letter to Pakistan prime minister Imran Khan|
|US Open comes too soon for Tsonga|
|Unpredictable results making 2018 F1 season a classic - Wolff|
|Mendy restricts phone use on Guardiola advice|
|Modric brands Inter approach claim ´the greatest nonsense in history´|
|Runners and Ryders: Olesen leapfrogs Poulter into last Team Europe berth|
|Kenedy escapes further action over Camarasa kick|
|England´s Bairstow suffers ´small fracture´ to finger|
|Gonalons joins Sevilla on loan from Roma|
|Modric, Ronaldo and Salah final UEFA Player of the Year nominees|
|Tottenham to play opening Champions League home match at Wembley|
|Karius´ Champions League blunders did not lead to Alisson signing - Klopp|
|Leeds considered €20m Conte offer before turning to Bielsa|
|Modric, Rakitic lead new era for World Cup finalists Croatia|
|Storm´s Chambers banned for three weeks, Smith injury not serious|
|Porte to race Vuelta after recovering from Tour crash|
|The Career Golden Masters: A run-down of Djokovic´s magnificent record|
|Japan send home four basketball players from Asian Games amid prostitution scandal|
|Rugby tackle bags helping Liverpool´s Alisson with Premier League life|
|Federer raring to go at US Open after Djokovic defeat|
|Chelsea boss Sarri plans to give up smoking|
|Alonso´s Toyota team stripped of Silverstone victory|
|Ceballos: No issue with former Real Madrid boss Zidane|
|MLS Review: Martinez equals single-season goalscoring record|
|Astros avoid sweep with win over Athletics|
|Seppi advances, Paire exits Winston-Salem|
|Bale feeling good as Madrid eye sweep of trophies|
|You can´t leave a house three-quarters built – Neville urges United to back Mourinho|
|Dodgers slugger Machado leaves game after being struck by pitch|
|Harden says Carmelo will ´be a good fit´ for Rockets|
|Morata: I never considered Chelsea exit|
|Gavrilova kicks off title defence in New Haven|
|Lopetegui pleased with Bale and Real Madrid after LaLiga opener|
|It´s a very special moment – Djokovic revels in Golden Masters achievement|
|Sorrentino thanks Ronaldo for support after injury|
|Twins place Santana on DL with finger injury|
|Yankees´ Gregorius suffers ´pretty significant´ heel bruise|
|Snedeker ends PGA Tour drought with Wyndham Championship win|