The Spanish motorcyclist Jorge Lorenzo benefited from a spectacular crash by compatriot Dani Pedrosa to win the US MotoGP and take his fourth victory in the past five races.
Pedrosa, who won last week's German Grand Prix, had powered ahead early on in the 32-lap race before crashing out on the fifth turn of lap 12.
Lorenzo finished more than three seconds ahead of the Australian Casey Stoner, to extend his world championship lead.
The defending MotoGP champion, Valentino Rossi, finished third in only his second race back after breaking a leg in practice for last month's Italian Grand Prix.