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.
|If you Googled ´European nights´, Liverpool would be top result - Klopp|
|BREAKING NEWS: Icardi cut from Argentina World Cup squad|
|Test recall a ´fantastic surprise´ for Buttler|
|Klopp needs Premier League to be a Liverpool great – Johnston|
|Salah is ´definitely´ world´s best - Lovren|
|Rhinos captain Watkins ruled out for eight months|
|No clue - Klopp defiant over Can to Juventus claims|
|Younis tips Babar for Pakistan greatness|
|Germany squad numbers hint at World Cup good news for Neuer|
|WATCH: Moto3 rider makes spectacular jump over crashed rival|
|Leaving out Morata ´painful´ for Spain boss Lopetegui|
|Gustard to leave England role for Harlequins|
|Nainggolan retires from Belgium duty after World Cup snub|
|Spain striker Morata misses out on World Cup selection|
|LeBron or Kawhi could lead Lakers to the Finals - World Peace|
|Serena steps up Roland Garros training ahead of French Open|
|Nainggolan left out of Belgium´s World Cup squad|
|The long goodbye: Iniesta sits alone in Camp Nou after final Barcelona match|
|Wane to leave Warriors at end of season|
|Dr Fury will see you now - Tyson plans future career in medicine|
|Harden, D´Antoni rue ´soft´ Rockets performance in Warriors drubbing|
|Liverpool players can change their lives in Kiev, says Gerrard|
|Real Madrid v Liverpool: Can great deeds of the past fuel the bid for Champions League glory?|
|Wash your mouth out! - Curry´s expletive outburst earns scolding from mother|
|Rakitic lost for words as Iniesta heads for Barcelona exit|
|Conte: Chelsea must overhaul squad to change style|
|Johnston: Liverpool can´t lose Suarez, Coutinho and Salah!|
|Messi: I like Griezmann, he´s one of the best|
|Ohtani says he´s not good enough for Home Run Derby yet|
|Mendy: France are eyeing World Cup glory|
|Scott accepts two-week ban for Walker punch|
|Braves rally for six runs in the ninth to defeat Marlins|
|MLS Review: Red Bulls upstage Atlanta thanks to Wright-Phillips brace|
|Warriors breeze past Rockets in game three|
|We have a quality squad – Man City chairman hints at caution in transfer market|
|Wise cruises to maiden PGA Tour victory at Byron Nelson|
|Matic: United can fight for Premier League and Champions League with experience|
|Golden Knights GM on Stanley Cup Finals berth: I don´t know how we did it|
|I did a ´s*** job´ defending LeBron James – Morris|
|Dembele suffers sprained right ankle|
|We know Fellaini´s not going to renew with United – Mirabelli suggests Milan move|
|Cavs´ Lue not satisfied with just one win|
|They even whistled at Torres – Simeone backs Griezmann|
|I arrived as a boy, I leave as a man – Iniesta in emotional Barcelona farewell|
|Lingard: Wembley loss my worst feeling in football|
|Cahill: Conte uncertainty affecting Chelsea|
|Sarri has run out of time – Napoli chief De Laurentiis|
|Barca boss Valverde salutes departing Iniesta|
|I feel like I´ve been run over by a truck or had 15 pints - Crutchlow|
|Four sent off as Ajaccio win chaotic Le Havre play-off on penalties|
|Sweden win shoot-out to retain world title|
|De Vrij penalty was destiny for Inter - Icardi|
|PSG? Maybe one day - Pogba coy over long-term future at Manchester United|
|Messi wins fifth European Golden Shoe|
|Gattuso calls for more malice at Milan|
|Barcelona 1 Real Sociedad 0: Coutinho stunner lights up Iniesta´s farewell|
|Lazio 2 Inter 3: Spalletti´s men seal Champions League qualification with stunning comeback|
|Royals reach play-offs as Kings XI come up short|
|Nadal sees clearly after Rome rain is gone|
|Double whammy for Zverevs as Mischa bows out in Geneva|
|Atletico Madrid pay fitting tribute to tearful Torres|
|Hull FC claim derby spoils, Dragons off the bottom|
|Buzarnescu battles through as McHale impresses in Nuremberg|
|Neymar an artist who will not need special treatment - new PSG coach Tuchel|
|Atletico Madrid 2 Eibar 2: Torres bows out with a double|
|Napoli 2 Crotone 1: Milik and Callejon condemn visitors to the drop|
|Iniesta starts on Barcelona goodbye but Messi rested|
|Nadal rallies after rain break to dethrone Zverev in Rome|
|AC Milan 5 Fiorentina 1: Cutrone brace secures Europa League group stage spot|
|I think I made a fantastic decision - Garoppolo key to Sherman joining 49ers|