Spain's Juan Antonio Flecha of iBanesto.com escaped with 13km left to snatch the 11th stage of the Tour de France from Narbonne to Toulouse.
Flecha attacked the eight-man breakaway and hung on for the win in three hours 29 minutes 33 seconds after racing for 153.5km.
He held off Isidro Nozal of ONCE and Rabobank's Bram de Groot by four seconds, with the remainder of the breakaway following on behind.
Cofidis rider Inigo Cuesta was fourth, 15 seconds back, with Carlos Da Cruz, Stuart O'Grady, Nicolas Portal and Michael Rogers all eight seconds further adrift.
Australian sprinter Robbie McEwen led home the main peloton - including yellow jersey Lance Armstrong - 42 seconds behind.
"It's incredible, but I want to dedicate my win to my
whole team," said Flecha, who is riding in his first Tour.
American Armstrong maintained his 21-second overall lead from Telekom rider Alexandre Vinokourov.
Friday's 12th stage is a 41.5km individual time trial - where the riders race against the clock - from Gaillac in the Tarn region to Cap' Decouverte.
It could prove crucial to Armstrong's chances of claiming a record-equalling fifth victory.
"It's a big day for me and for the race," said Armstrong of
the time trial.
"It may well be the most important time trial in
the last five Tours because the race is so tight.
"I know the course well and I like it. We'll see how it
It is followed by three gruelling mountain stages in the Pyrenees.
The 171 riders left in the race rolled out of the Roman city of Narbonne in the south of France under a sweltering sun at 1230 BST.
Immediately, the peloton was driven quickly by the US Postal team as a handful of speculative attacks came and went.
After just over an hour, the main eight-man breakaway went clear and were able to consolidate their gap, stretching the lead to as much as four minutes.
Flecha attacked the leading group with just over 10km left to race and as his pursuers struggled to organise the chase, he made good his escape.