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.
|Allegri pleased with Ronaldo despite goalless Juventus debut|
|Chelsea can produce magic with Sarri in charge - Hazard|
|Emery ´happy without the result´ as Arsenal comeback falls short|
|Gordon confirms Cleveland Browns return|
|Eight shots and only 30 passes - Ronaldo´s Juventus debut in Opta numbers|
|Cristiano Ronaldo´s debuts: Best impressed, scoring a penalty & a blank for Juventus|
|Old boy Escare haunts Catalans in big Wigan win|
|Preston North End 2 Stoke City 2: Super sub Crouch salvages a point|
|Pochettino vows not to discuss Alderweireld future before five-minute answer|
|Waring, Aiken lead the way as Olesen stays in the hunt|
|Linking play, forcing saves and clashing with goalkeeper - Cristiano Ronaldo´s Juventus debut|
|Chelsea 3 Arsenal 2: Alonso snatches win after Gunners comeback|
|West Ham still haunted by last season - Pellegrini|
|Puel defends Vardy after Wolves red card|
|Chievo 2 Juventus 3: Ronaldo´s debut ends in dramatic win|
|Mbappe: Neymar is Paris Saint-Germain´s superstar|
|Pickford should have seen red - Hughes fumes over challenge on Ings|
|Kohli and Rahane star as India edge day one|
|AC Milan´s Strinic sidelined by heart problem|
|Kane happy to banish August goal hoodoo|
|Guingamp 1 Paris Saint-Germain 3: Mbappe returns to inspire comeback|
|Springboks´ second-half revival punishes Pumas|
|Finally! Kane scores a Premier League goal in August|
|Warnock enjoyed ´poetic justice´ of Kenedy´s penalty woe|
|Holders Eintracht Frankfurt stunned by Ulm in DFB-Pokal|
|West Ham 1 Bournemouth 2: Wilson, Cook condemn Hammers to successive losses|
|Tottenham 3 Fulham 1: Trippier and Kane help Spurs avoid Wembley wobble|
|Leicester City 2 Wolves 0: Lucky Foxes win despite Vardy red card|
|Everton 2 Southampton 1: Richarlison continues fine start|
|Drochtersen/Assel 0 Bayern Munich 1: Lewandowski spares Bayern´s blushes|
|Violent hack, no passes, missed penalty - Kenedy´s Cardiff nightmare|
|Ronaldo handed Juventus debut against Chievo|
|Cheika and Hooper frustrated by second-half slump|
|Hansen issues warning after All Blacks win Wallabies ´prizefight´|
|Stuttgart stay good for Pavard, says Reschke|
|You can´t buy class - United boss Mourinho blasts City documentary|
|Cardiff City 0 Newcastle United 0: Penalty miss rounds off abject day for Kenedy|
|Lopetegui open to rotating Real Madrid goalkeepers|
|´World´s best´ Alisson will be difficult to replace, says Roma boss Di Francesco|
|Dragons and Sharks pounce on Panthers after four get sin-binned|
|AC Milan situation has proved FFP works - UEFA president Ceferin|
|Marseille´s Garcia uninterested in striker despite Balotelli link|
|Goodhue sparkles on debut as All Blacks thump Wallabies|
|I feel like chicken tonight - Saunders game for a laugh after Wilder fowl play|
|Aubameyang-Lacazette partnership possible for Arsenal|
|Pant handed debut as India ring changes at Trent Bridge|
|Pochettino pledges to protect Kane|
|Federer relieved to ´hang tough´ in Cincinnati|
|De Bruyne injury: Can Foden or Diaz replace Man City playmaker?|
|Furyk confident as Team USA takes shape|
|Neymar´s behaviour deserves praise, Tite claims|
|Scherzer, Harper lead Nationals past Marlins|
|Djokovic and Federer join Cilic, Goffin in Cincinnati semis|
|Federer outlasts recovering Wawrinka|
|WATCH: Djokovic wins match, loses car|
|Bolt arrives in Sydney for A-League trial|
|Red-hot Bertens beats Svitolina, Halep marches on|
|Snedeker preserves Wyndham lead|
|Halep hits back to torment Tsurenko|
|Raonic fails to break Djokovic stranglehold|
|Emery seeks more ´demanding´ Ozil|
|CAF Champions League Review: Wydad, Al Ahly & TP Mazembe qualify|
|Stephen Curry wants to finish his career with Warriors|
|Hazard among Europe´s best but can improve, says Sarri|
|Tigers boost top-two hopes, Giants close in on fourth|
|Birmingham City 0 Swansea City 0: Monk´s men held despite dominance|
|Inter taking legal action against Tebas over Modric transfer comments|
|Serie A transfer round-up: Zaza joins Torino, Parma sign Gervinho|
|Roma chief Pallotta makes light of De Laurentiis claim|
|Federer starts double-header by seeing off resilient Mayer|