The Wuerth rider was part of the decisive breakaway on the 166-km stage and then attacked alone on the final Gotthardpass climb.

Spain's David Herrero finished second, 34 seconds behind Contador, with Australia's Cadel Evans third.

Koldo Gil of the Saunier Duval team retained the overall race lead.

Stage result:
1. Alberto Contador (Spain / Wuerth ) 4:19:03"
2. David Herrero (Spain / Euskaltel ) +34"
3. Cadel Evans (Australia / Davitamon - Lotto )
4. Alexandre Moos (Switzerland / Phonak ) +37"
5. Koldo Gil (Spain / Saunier Duval )
6. Alexandre Botcharov (Russia / Credit Agricole )
7. Jan Ullrich (Germany / T-Mobile )
8. Linus Gerdemann (Germany / T-Mobile )
9. Joerg Jaksche (Germany / Wuerth )
10. Andy Schleck (Luxembourg / Team CSC )

General classification:
1. Koldo Gil (Spain / Saunier Duval ) 37:42:01"
2. Joerg Jaksche (Germany / Wuerth ) +30"
3. Jan Ullrich (Germany / T-Mobile ) +50"
4. Angel Vicioso (Spain / Wuerth ) +2:03"
5. Andy Schleck (Luxembourg / Team CSC ) +2:22"
6. Janez Brajkovic (Slovenia / Discovery Channel ) +2:36"
7. Giampaolo Caruso (Italy / Wuerth ) +2:45"
8. Linus Gerdemann (Germany / T-Mobile ) +3:30"
9. Alexandre Botcharov (Russia / Credit Agricole ) +3:42"
10. Vladimir Karpets (Russia / Caisse d'Epargne ) +4:15"