Dani Pedrosa ended MotoGP title leader Jorge Lorenzo's run of five consecutive pole positions during a dramatic qualifying session at Brno in the Czech Republic.
Lorenzo and Fiat Yamaha team-mate Valentino Rossi both finished the session on foot, having crashed out in separate incidents in the closing stages.
Lorenzo fell first, lowsiding from his factory M1, which then skipped across the gravel and vaulted onto the top of a tyre barrier.
The Spaniard was unharmed and briskly walked to his machine to switch off the engine, in an attempt to limit any engine damage.
Rossi's accident was less spectacular, the Italian slipping off after losing the front into the final chicane.
The reigning seven time MotoGP champion, who broke his leg in June, was visibly furious with the error which has left him fifth on the grid.
Meanwhile, Rossi's rumoured 2011 replacement Ben Spies had led the Yamaha challenge for much of the second half of the session, first taking pole with 17 minutes to go, then putting his Monster Yamaha Tech 3 back on top with five minutes remaining.
The MotoGP rookie, who won a World Superbike race at Brno last season, was eventually denied pole by a last-minute lunge from Pedrosa, which put the Repsol Honda rider 0.338sec clear for his third pole of the season.
Second for Spies is still his best grand prix qualifying to date, and first ever front row, while Lorenzo - who crashed out of last year's race while battling with Rossi - will start alongside him in third place.
Pedrosa and Lorenzo had an arm-waving moment after a near collision 20 minutes into the session, after Lorenzo tried to go around the outside of the #26.