American Floyd Landis took over the Tour de France yellow jersey on Thursday after Russian Denis Menchov won the tough 206.5-km 11th stage through the Pyrenees which caught out several leading riders.
After over six hours in the saddle, Menchov outsprinted American Levi Leipheimer and compatriot Landis.
Landis relieved Frenchman Cyril Dessel of the leader's jersey thanks to bonus points.
Dessel, who came home in 18th at four minutes 45 seconds behind Menchov, is now second overall, eight seconds behind Landis with Menchov in third at 1:01.
Landis, who announced on Monday he would undergo hip surgery after the Tour, said: "I would just as soon have waited to get the yellow jersey and race easy just to let someone else do the work but you can't turn down the chance."
Landis, a former lieutenant of Lance Armstrong, quit Discovery Channel to join Phonak in 2005.
On an exhausting stage, the decisive battle was waged on the final ascent, the first-category Pla-de-Beret.
Menchov, Leipheimer and Landis were among the first group of eight riders to reach the 7.5-km slope which has an average gradient of 5.5 percent.
Christophe Moreau of France, Andreas Kloeden of Germany and Michael Boogerd of the Netherlands were soon dropped, followed by Spaniard Carlos Sastre and Australian Cadel Evans.
Menchov, Leipheimer and Landis were left to force their way between two undulating walls of orange-clad Spanish supporters.
Spaniard David De La Fuente claimed the best climber's polka-dot jersey from Dessel after breaking away with three other riders.
The arduous high mountain passes and the heat took their toll on big names such as Italian Paolo Savoldelli, winner of the Giro d'Italia in 2005, and Ukraine's Yaroslav Popovych.
In addition, Discovery Channel leader George Hincapie finished 21 minutes off the pace and Euskaltel's Iban Mayo, sixth overall in the 2003 Tour, struggled from the Tourmalet and, deserted by his team mates, finally pulled out.
Friday's 211.5-km 12th stage is from Luchon to Carcassonne.