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.
16. August 2018
|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´|
15. August 2018
|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|
|All Blacks stick with Barrett as Mo´unga misses out altogether|
|Modric benched for UEFA Super Cup clash with Atletico Madrid|
|Cipriani charged with assault after Jersey nightclub incident|
|Hamburg 1 Bayern Munich 4: Wagner and Muller hit braces in comeback victory|
|WATCH: Messi scores first goal as Barcelona captain|
|Iniesta, Xavi and Puyol were great teachers, says new Barcelona captain Messi|
|Moses retires from international football|
|Goals, assists, set-pieces - The stats that show De Bruyne is almost irreplaceable for City|
|Bergeron wins mammoth 24-man U.S. Amateur play-off|
|Hart to Burnley "not rocket science", says Dyche|
|Leipzig, Schalke reject Rudy transfer rumours|
|Yedlin knee injury not serious, Newcastle confirm|
|Bartomeu satisfied with Barcelona squad amid Pogba links|
|Kevin De Bruyne suffers knee injury|
|Steelers QB Roethlisberger in concussion protocol|
|Kehrer to PSG not complete, say Schalke|
|Hopoate handed 10-year ban from NSWRL|
|Is this worth it? Injuries prompted Te´o to consider future|
|Croatia hero Subasic retires from international football|
|Iniesta makes it two in two for Vissel Kobe|
|Chelsea send out defensive duo on loan|
|Zaha 2023: Palace star means more than goals|
|De Jong set for Ajax stay despite Barcelona interest|
|Serena ´still at the very beginning´ of comeback|
|Ajax can benefit from Mourinho approach - Blind|
|Foley not convinced by reports All Blacks will drop Barrett|
|Zaha signs Crystal Palace extension|
|Burnley midfielder O´Neill makes A-League loan move|
|Godin yet to renew with Atletico Madrid amid transfer interest|
|Federer ´feeling better every day´ after Wimbledon disappointment|
|Kante comfortable with surprise new Chelsea role|
|Rugby Championship 2018: The numbers behind New Zealand´s dominance|
|LaLiga 2018-19: Bale ready to be Madrid´s shining light after five years in Ronaldo´s shadow|
|Rodgers unimpressed by absence of ´fit´ Boyata|
|Braves´ Acuna Jr. has arrived as a true MLB star|
|LA Galaxy 2 Colorado Rapids 2: Jackson´s deflected strike sees spoils shared|
|Victory offer postponed retirement, says Honda|
|Kyrgios forgets tennis shoes, Federer back in business|
|Williams knocked out as Garcia and Pliskova advance in Ohio|
|Kvitova sees off Serena in Cincinnati classic|
|Federer dispatches Gojowczyk in Cincinnati|
|Stead succeeds Hesson as New Zealand coach|
|Duminy encouraged despite South Africa´s mixed results|
|Thiem withdraws from Cincinnati Masters|
|Edwards joins Ospreys in consultancy role|
|Former Arsenal and Barcelona player Song joins Sion|