Andy Schleck made his claim for Tour de France victory with a solo surge to win at the highest summit finish in the race's history, but Thomas Voeckler retained the yellow jersey for a 10th day with another resilient performance.
The 200.5-kilometre 18th stage from Pinerolo returned to France, finishing at Galibier Serre-Chevalier - at an altitude of 2,645metres - and presented an opportunity for the overall favourites to attack.
Andy Schleck (Leopard Trek), runner-up to Alberto Contador in each of the last two years, did just that but could not end Voeckler's stint in the yellow jersey.
Ireland's Nicolas Roche was part of a midway break and was in third position at one stage, but he dropped back towards the end and finished in 19th place, 4:58 behind Schlek.
Schleck began the day two minutes 36 seconds behind Frenchman Voeckler (Europcar) and attacked on the 14.1km Col d'Izoard to distance himself from the yellow jersey group, which included the other overall favourites.
He forged forward, catching the remnants of the day's breakaway before his high tempo up the hors categorie (beyond category) Col du Galibier saw him solo to a third Tour stage win.
Frank Schleck (Leopard Trek) was second, 2mins 07secs behind his brother, and Cadel Evans (BMC Racing) was 2:15 behind, while Voeckler was 2:21 adrift in fifth to stay in the maillot jaune by 15 seconds from Andy Schleck.
Defending champion Contador (Saxo Bank-SunGard) was not so lucky, finishing 3:50 down in 15th place and now sits seventh, 4:44 behind Voeckler with three days of racing remaining.
Roche is in 19th position overall, 16:43 behind Voeckler.
