World championship leader Jorge Lorenzo won the San Marino MotoGP to extend his lead in the standings while his nearest challenger and fellow Spaniard Dani Pedrosa crashed early in the race in Misano.
Honda rider Pedrosa collided with Karel Abraham, causing both riders to crash out, with the pair of them lucky to walk away unscathed.
Italy's Valentino Rossi was second, just ahead of Alvaro Bautista.
Australian world champion Casey Stoner, third in the overall standings, is out of action after undergoing surgery on his ankle in August.
On an emotional day both Rossi and Bautista dedicated their finishes to the late Marco Simoncelli, who was killed in the Malaysian MotoGP last year and after whom the circuit here is now named.
Lorenzo had begun the day only 13 points ahead of Pedrosa but the Honda rider was taken out of the race on the first lap by accident-prone Hector Barbera.
Pedrosa had a nightmare, having to start from the back of the grid because of brake problems on the warm-up lap after he qualified in pole.
Lorenzo leads Pedrosa by 38 points with five races remaining.
"To be honest I couldn't see the board very clearly and I thought Bautista was out not Pedrosa," said Lorenzo.
"It is bad luck for Honda but a great result for us. I am very happy to finally have the luck come down on our side."
Rossi, who joins Lorenzo next season at Yamaha, was delighted to have equalled his season best performance - though his previous second place came in the rain-affected French MotoGP.
"I think this second place is something special," said the 33-year-old.
"First because it is in Misano which is very close to my home town and secondly the circuit is in the name of Marco (Simoncelli) and I dedicate this runners-up position to him and his family."
Bautista was ecstatic at recording his first podium finish in MotoGP especially as it was for the Gresini team that Simoncelli rode for.
"I am emotional for sure," the 27-year-old said. "My first ever podium finish is very special. I am so happy. This is in memory of Marco."
Lorenzo had no problems at the start easing away while Rossi had a super start, surging into second, and Stefan Bradl also passed Cal Crutchlow who later in the lap was overtaken by team-mate Andrea Dovizioso.
Crutchlow's determination to regain the places he had lost on the first lap ended badly as with 23 laps remaining he slid off and was left clutching his knee.
Bradl began to close on Rossi with 15 laps remaining while Dovizios also took closer order but it was Bautista who was making the most progress with a succession of fastest lap times on his Honda.
Bautista passed Dovizioso into fourth with 11 laps to go and set off in pursuit of Bradl and Rossi with Lorenzo out on his own nearly six seconds clear.
Bautista's remorseless momentum saw him then get the better of Bradl with nine laps to the finish and five laps later both Dovizioso and American Yamaha rider Ben Spies overtook a weakening Bradl.