Reigning WorldSBK Champion Jonathan Rea fended off an early challenge from poleman Chaz Davies to take the race one win at Laguna Seca and extend his championship lead to 70 points.
Davies took the holeshot from pole and the pair pulled a big gap early on but a small mistake at the top of the Corkscrew from the Aruba Ducati man allowed Rea through to take victory by a second with Alex Lowes in a lonely third place.
Lowes passed front row qualifier Tom Sykes (Kawasaki Racing Team) for third place early in the race, and Lowes held that position all the way to the flag for his tenth career podium.
Sykes at times went over two seconds slower than the top pace, and finally succumbed to Eugene Laverty (Milwaukee Aprilia), Marco Melandri (Aruba.it Racing – Ducati) and Xavi Fores (Barni Racing Team Ducati), who finished fourth, fifth and sixth respectively.
In seventh Sykes had to fight a final rearguard action to keep that position from the advancing Michael van der Mark (Pata Yamaha Official WorldSBK).
Jordi Torres (MV Agusta Reparto Corse) placed ninth and after Leon Camier (Red Bull Honda World Superbike Team) stopped with a technical issue, Jake Gagne (Red Bull Honda World Superbike Team) finished tenth at his home round and was the top Honda man.
PJ Jacobsen (TripleM Honda World Superbike Team) fell after a tussle with Leandro Mercado (Orelac Racing VerdNatura Kawasaki), and the Kawasaki rider would fall himself shortly afterwards.
Early top five runner Lorenzo Savadori (Milwaukee Aprilia) fell on lap two, at the apex of the final corner, finishing up 14th.
Toprak Razgatlioglu (Kawasaki Puccetti Racing) had a big crash down The Corkscrew and was taken for checks in the medical centre.
Josh Herrin (Attack Performance Two Wheel Legal Yamaha) retired.