Alcaniz - MotoGP leader Casey Stoner took his ninth pole position of the season at the Aragon Grand Prix on Saturday, while world champion Jorge Lorenzo finished fourth.
Stoner rode his Honda around the 5km MotorLand Aragon Circuit in 1 minute, 48.451 seconds.
Dani Pedrosa of Spain will start Sunday's race second on the grid with Ben Spies of the United States third.
Valentino Rossi continued his difficult season by crashing early in the session. The seven-time MotoGP champion returned to finish in 13th place.
Stoner, who won last year's Aragon GP starting from pole, leads Lorenzo by 35 points in the overall standings with five races to go.
In the Moto2 category, Marc Marquez won the pole with a fastest lap of 1:53.296, while fellow Spaniard Julian Simon was second. Britain's Scott Redding was third.
In the 125cc class, Hector Faubel earned his first pole of the season after setting a track record of 1:59.222. Maverick Vinales and Nicolas Terol completed a Spanish sweep of the top three spots.
Qualifying results on Saturday for Sunday's Aragon Grand Prix:
MotoGP
1. Casey Stoner, Australia, Honda, 1 minute, 48.451 seconds.
2. Dani Pedrosa, Spain, Honda, 1:48.747.
3. Ben Spies, United States, Yamaha, 1:49.155.
4. Jorge Lorenzo, Spain, Yamaha, 1:49.270.
5. Andrea Dovizioso, Italy, Honda, 1:49.372.
6. Marco Simoncelli, Italy, Honda, 1:49.528.
7. Nicky Hayden, United States, Ducati, 1:49.752.
8. Karel Abraham, Czech Republic, Ducati, 1:49.777.
9. Hiroshi Aoyama, Japan, Honda, 1:49.813.
10. Randy De Puniet, France, Ducati 1:49.826.
125cc
1. Hector Faubel, Spain, Aprilia, 1 minute, 59.222 seconds.
2. Maverick Vinales, Spain, Aprilia, 1:59.231.
3. Nicolas Terol, Spain, Aprilia, 1:59.365.
4. Johann Zarco, France, Derbi, 1:59.598.
5. Danny Kent, Great Britain, Aprilia, 1:59.814.
6. Luis Salom, Spain, Aprilia, 1:59.902.
7. Sandro Cortese, Germany, Aprilia, 2:00.011.
8. Alberto Moncayo, Spain, Aprilia, 2:00.316.
9. Efren Vazquez, Spain, Derbi, 2:00.432.
10. Jonas Folger, Germany Aprilia, 2:00.447.