Marco Simoncelli was quickest in opening free practice for the German Grand Prix at the Sachsenring, amid a string of crashes for leading riders.
Championship leader Casey Stoner (Honda), his team-mate Dani Pedrosa, Ducati's Valentino Rossi and LCR Honda rider Toni Elias all lost control and fell at the downhill right-hander at Turn 11.
Rossi's was the most violent of the accidents, the former champion tumbling heavily through the gravel and having to go to the medical centre for checks. But he escaped with just cuts to his arm.
Elias would later have a second, much heavier, crash at Turn 1 having resumed on his spare bike, ending his morning.
Simoncelli avoided the carnage and set a session-best time of 1m22.823s on the Gresini Honda.
Stoner improved to second right at the end, 0.181 seconds down on the Italian, and 0.042s ahead of his main title rival Jorge Lorenzo's Yamaha.
Nicky Hayden was an encouraging fourth for Ducati, with satellite Ducati riders Karel Abraham (Cardion AB), Hector Barbera (Aspar) and Randy de Puniet (Pramac) also looking strong in sixth to eighth places, behind works Honda man Andrea Dovizioso.
The works and Tech 3 Yamahas of Ben Spies and Colin Edwards completed the top 10, while Pedrosa - who had been as high as second - fell to 11th following his crash.
Pos Rider Team/Bike Time Gap 1. Marco Simoncelli Gresini Honda 1m22.823s 2. Casey Stoner Honda 1m23.004s + 0.181s 3. Jorge Lorenzo Yamaha 1m23.046s + 0.223s 4. Nicky Hayden Ducati 1m23.205s + 0.382s 5. Andrea Dovizioso Honda 1m23.355s + 0.532s 6. Karel Abraham Cardion Ducati 1m23.416s + 0.593s 7. Hector Barbera Aspar Ducati 1m23.433s + 0.610s 8. Randy de Puniet Pramac Ducati 1m23.534s + 0.711s 9. Ben Spies Yamaha 1m23.558s + 0.735s 10. Colin Edwards Tech 3 Yamaha 1m23.594s + 0.771s 11. Dani Pedrosa Honda 1m23.604s + 0.781s 12. Alvaro Bautista Suzuki 1m23.989s + 1.166s 13. Cal Crutchlow Tech 3 Yamaha 1m24.162s + 1.339s 14. Valentino Rossi Ducati 1m24.512s + 1.689s 15. Hiroshi Aoyama Gresini Honda 1m24.620s + 1.797s 16. Toni Elias LCR Honda 1m26.060s + 3.237s 17. Loris Capirossi Pramac Ducati 1m26.334s + 3.511s