Kazakhstan's Alexandre Vinokourov won the second alpine leg of the 21-stage race in 4 hours, 47 minutes and 38 seconds. Santiago Botero of Colombia came in second, followed by Christophe Moreau of France on the 107.5-mile course that ended in Briancon.
Overall, Armstrong, who is seeking a seventh consecutive victory in the world most famous bike race, has a 38-second lead over Denmark's Mickael Rasmussen. Moreau, who is 2 minutes, 34 seconds back, is third.
Thursday's 12th stage turns southward toward Provence in a 116-mile trek from Briancon to Digne-les-Bains.