Jonathan Rea saw off the charge of his Kawasaki team-mate Tom Sykes to claim the honours in Race 1 at Laguna Seca.
Nicky Hayden continued to impress in his debut season, with the American putting his Honda on the podium in a great exhibition of riding under pressure.
Sykes made the most of his pole position to take the first corner in the lead with Chaz Davies second after the opening lap excitement had died down, with the Welshman getting the jump on Rea and Davide Giugliano to move up from fourth on the grid.
The Aruba.it Racing Ducati rider hit the front with 21 laps to go, but his early gains came to an end when he pushed too hard and slid into the gravel at Turn 6, ending his chances of a podium finish. To make matters worse for the Ducati outfit, Giugliano would later find the gravel too.
Rea was the man to take advantage, but the Ulsterman had to work for his maiden victory at the California track after an error at the Corkscrew bend saw him drop behind Sykes. Rea would not be denied though, and finished a second ahead of his team-mate.
The Kentucky Kid Hayden notched up his third podium finish of the campaign, adding to the third place he registered at Assen before winning Race 2 at Sepang.
1. Jonathan Rea GBR Kawasaki Racing ZX-10R 25 laps
2. Tom Sykes GBR Kawasaki Racing ZX-10R 0.819s
3. Nicky Hayden USA Honda Racing CBR1000RR 12.296s
4. Michael van der Mark NED Honda Racing CBR1000RR 13.067s
5. Alex Lowes GBR PATA Crescent Yamaha R1 13.335s
6. Lorenzo Savadori ITA IodaRacing Aprilia RSV4 13.816s
7. Xavi Fores ESP Barni Ducati 1199R 15.541s
8. Jordi Torres ESP Althea BMW S1000RR 15.838s
9. Alex de Angelis RSM IodaRacing Aprilia RSV4 19.999s
10. Niccolo Canepa ITA Pata Crescent Yamaha R1 22.832s
11. Leon Camier GBR MV Agusta RC F4 RR 24.065s
12. Anthony West FRA Pedercini Kawasaki ZX-10R 28.902s
13. Josh Brookes AUS Milwaukee BMW S1000RR 39.957s
14. Karel Abraham CZE Milwaukee BMW S1000RR 46.552s
15. Roman Ramos ESP GO Eleven Kawasaki ZX-10R 55.791s
16. Dominic Schmitter SUI Grillini Kawasaki ZX-10R 59.021s
17. Peter Sebestyen POL Team Toth Yamaha R1 1 lap
18. Pawal Szkopek POL Team Toth Yamaha R1 1 lap
Did not finish
Saeed al Sulaiti QAT Pedercini Kawasaki ZX-10R 16 laps completed
Gianluca Vizziello RSA Grillini Kawasaki ZX-10R 16 laps completed
Davide Giugliano ITA Aruba.it Racing Ducati 1199R 12 laps completed
Raffaele De Rosa ITA Althea BMW S1000RR 12 laps completed
Chaz Davies GBR Aruba.it Racing Ducati 1199R 4 laps completed