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 felt like Benjamin Button – Ibrahimovic misses ´fantastic´ Pogba and Man United team-mates|
|I should have faced Mourinho – Casillas rues Real Madrid fall-out|
|Kubica handed Williams drive for 2019|
|Hansen rings the changes for Italy clash|
|Zabaleta: West Ham need Nasri´s quality|
|Atletico Madrid v Barcelona: 2018-19 signings compared|
|Guardiola can repeat Barcelona success at Man City - Xavi|
|Harris not worried about previous Langer criticism|
|Blazers routed by Bucks, Warriors lose again|
|Nowitzki looking at December return after long recovery from ankle surgery|
|Australia, England and South Korea share World Cup of Golf lead|
|Warm welcome from Cavs ´means a lot´ to LeBron|
|LeBron helps Lakers past Cavs in Cleveland return|
|Guardiola: Premier League has improved me as a manager|
|WATCH: Cavs´ tribute video for LeBron does him justice in return to Cleveland|
|Harris, Tremain earn Australia Test spots|
|Mourinho would´ve won titles at Man City – Drogba|
|Cowboys WR Gallup set to play on Thursday after death of brother|
|Sutton re-signs with Rabbitohs for 2019|
|Chelsea legend Drogba confirms retirement at 40|
|England on track to be the world´s best in Tests - Root|
|Aubameyang ´trying to get fit´ for Bournemouth clash|
|Tenerife streak halted by PAOK as Bologna roll on|
|FIFA president Infantino pledges best ever World Cup in Qatar|
|India favourites after ´one of the worst years´ for Australia - Warne|
|Klaassen: Impossible to compare me to Kroos, Xavi|
|Guardiola eyeing future international job|
|Trubisky doubtful for Bears´ Thanksgiving game|
|O´Neill planning ´next adventure´ after leaving Republic of Ireland|
|Premier League: Brexit should not be used to weaken squads|
|16 balls, 14 boundaries, 74 runs - Shahzad steals show in T10 opener|
|WATCH: Patrice Evra plays with poultry in bizarre Thanksgiving message|
|Packers star Rodgers pledges $1m to California wildfire relief|
|Klitschko worried for boxing´s Olympic future|
|Lewandowski back in Bayern training as Davies joins new team-mates|
|Hogg fit for much-changed Scotland|
|Former Arsenal striker Bendtner faces 50 days in prison over taxi driver assault|
|Athletic extend Muniain contract to 2024|
|Kohli ready to move on after narrow defeat|
|PSG to wait for Neymar, Mbappe injury updates|
|Icardi hopeful of Messi return for Copa America|
|Cavs star Love expects to be out until 2019|
|Ricciardo terrified by Renault switch|
|Under-fire Taylor calls for PFA structure review|
|McLaren reveal one-off livery for Alonso´s last race|
|Samir Nasri training with West Ham amid reports of free transfer|
|Guardiola warned over derby clash comments|
|Stoinis sees Australia to T20 win against India|
|Modric not deserving of Ballon d´Or – Cavani|
|F1 Raceweek: Alonso ends on 312 races, Raikkonen a Ferrari great - Abu Dhabi GP in numbers|
|Neymar made a mistake leaving Barcelona for PSG, insists Edmilson|
|O´Neill and Keane leave Republic of Ireland after relegation|
|WATCH: Maxwell hits Spidercam with sliced shot in Australia-India T20|
|Rafinha wants Barca exit due to ´crazy´ Valverde selections – Mazinho|
|France to wear rainbow laces in support of Thomas following attack|
|You need to stop this – Cavani slams media over supposed Neymar feud|
|Anderson rested for final Test|
|Tite applauds Seedorf for Cameroon´s style of play|
|Griezmann not obsessed with Ballon d´Or|
|Neymar feels injury is ´nothing serious´|
|Durant says Green altercation won´t impact his free agency|
|Morris blasts drama surrounding Wizards: It´s messed up|
|Scaloni thrilled for Dybala, Icardi|
|Green´s last-second shot keeps Raptors atop East standings|
|Deschamps praises Griezmann for Giroud gesture|
|Warriors star Curry improving, still out at least three more games|
|Chile 4 Honduras 1: Sanchez, Vidal shine for La Roja|
|Argentina 2 Mexico 0: Icardi, Dybala score first international goals|
|Mickelson calls Tiger the greatest of all time|
|Durant fined $25,000 for using inappropriate language|