Frenchman Cyril Dessel claimed the overall lead in the Tour de France after finishing second to Spaniard Juan Miguel Mercado on Wednesday's stage 10.
Dessel is the fifth different rider to wear yellow in this year's Tour
Mercado pipped Dessel in a sprint finish in the first Pyrenean mountain stage to take his second Tour stage victory, after a previous win in 2003.
He moved up to second overall behind Dessel, who also took the polka dot jersey for the King of the Mountains.
Previous yellow jersey holder Serhiy Honchar dropped to third overall.
Dessel, of AG2R-Prevoyance, started the day in 28th place overall, 3:50 adrift of the Ukrainian before the 190.5km from Cambo-les-Bains to Pau.
He became the first Frenchman to don the yellow jersey since Thomas Voeckler in 2004.
"I can be satisfied with my day even if I didn't win the stage", he said.
"I didn't want to let Mercado win because a stage win in the Tour is something rare. If I had won the stage it would have been a perfect day."
Dessel and Agritubel leader Mercado were among a group of 15 riders who broke away around the 40km mark, just before the first climb of the day, the third-category Col d'Osquich.
But that was just a warm-up before the hors category Col du Soudet - a long ascent on a narrow road thronged with thousands of spectators, with a 10% gradient over the last kilometre.
Specialist climber Iban Mayo, sixth overall in 2003, was one of many riders who cracked, along with Belgian world champion Tom Boonen, and prologue winner Thor Hushovd.
They all finished the stage in the last group, more than 24 minutes off the pace.
Dessel outsprinted Mercado at the top and again at the summit of the even steeper Col de Marie Blanque, after the duo launched a lung-bursting attack that proved decisive.
Dessel did all the hard work over the last 10km but Mercado timed his sprint to perfection over the last 200m as the duo crossed the line 56 seconds ahead of third-placed Inigo Landaluze, and more than seven minutes in front of the peloton including the former race leader Honchar.
Mercado (right) out-sprinted Dessel in the last 200m to take the victory
The main overall contenders are expected to start making a move in Thursday's 11th stage - a tortuous 206.5 kms from Tarbes featuring five climbs over some of the most famous Pyrenean passes.
The riders will cross into Spain for the last 16km, including the last ascent to the finish at the summit of the Plat-de-Beret.
American Floyd Landis is fifth overall, 4:45 behind, German Andreas Kloden is ninth, 5:35 back, while Australian Cadel Evans is 11th, 5:37 adrift.
Results from stage 10:
1. Juan Miguel Mercado (Spa/Agritubel) 4:49:10"
2. Cyril Dessel (Fra/AG2R) same time
3. Inigo Landaluze (Spa/ Euskaltel) +56"
4. Cristian Moreni (Ita/Cofidis) +2:24"
5. Christophe Rinero (Fra/Saunier Duval) +2:25"
6. Inaki Isasi (Spa/Euskaltel) +5:03"
7. Cedric Vasseur (Fra/Quick-Step) +5:35"
8. Daniele Bennati (Ita/Lampre) +7:23"
9. Erik Zabel (Ger/Milram) same time
10. Stefano Garzelli (Ita/Liquigas) same time
90. David Millar (Gbr/Saunier Duval) +12:00
152. Bradley Wiggins (Gbr/Cofidis) +24:24
1. Cyril Dessel (Fra/AG2R) 43 hours 07 mins 05 secs
2. Juan Miguel Mercado (Spa/Agritubel) +2:34"
3. Serhiy Honchar (Ukr/T-Mobile) +3:45"
4. Cristian Moreni (Ita/Cofidis) +3:51"
5. Floyd Landis (US/Phonak) +4:45"
6. Michael Rogers (Aus/T-Mobile) +4:53"
7. Inigo Landaluze (Spa/Euskaltel) +5:22"
8. Patrik Sinkewitz (Ger/T-Mobile) +5:30"
9. Andreas Kloeden (Ger/T-Mobile) +5:35"
10. Vladimir Karpets (Rus/Caisse d'Epargne) +5:37"
11. Cadel Evans (Aus/Davitamon-Lotto) +5:37"
68. David Millar (Gbr/Saunier Duval) +12:00
148. Bradley Wiggins (Gbr/Cofidis) +38:54