American Floyd Landis has lost the yellow jersey as leader of the Tour de France after being attacked on the final climb of stage 16.
Spaniard Oscar Pereiro was third behind Michael Rasmussen and Carlos Sastre to retake the lead overall.
Rasmussen won the stage after taking all four climbs to take the lead in the King of the Mountains standings.
CSC rider Sastre attacked Landis's group and the American came in 10 minutes three seconds behind Rasmussen.
LATEST UPDATES (all times BST)
1634: As Landis finally comes in, grey in the face, the finish went like this:
1. Michael Rasmussen Den/RAB
2. Carlos Sastre Esp/CSC at 1'41"
3. Oscar Pereiro Esp/Cd'E at 1'54"
4. Cadel Evans Aus/DVL at 1'56"
5. Andreas Kloden Ger/TMO at 1'56"
1631: Discovery's Jose Azevedo pedals across the line with the clock ticking past eight minutes, and still no Landis, who has dropped out of the top six in the general classification.
1629: Landis is being paced through the final stages by team-mate Axl Merckx, who has rejoined him on the climb. This has been an amazing day in the mountains.
1625: Sastre comes in just seconds ahead of Pereiro, who will be back in yellow tonight. Sastre will go second in the general classification.
1623: Rasmussen takes the stage, arms outstretched in celebration and agony.
1621: Landis is reportedly nine and a half minutes behind the lead group now. His yellow jersey is soaked with sweat and he can't seem to find a rhythm. Rasmussen goes under the flame rouge so just 1km left.
1618: Menchov is in agony now. Kloden is confirming the promise shown when he won the white jersey some years ago, Pereiro is proving wrong those who said he did not have the form to finish on the podium and Evans is once again in with the best in his second Tour.
1615: Kloden moves and Menchov almost literally falls out of his group. Kloden just has Pereiro and Cadel Evans with him now. Menchov falls in with Dessel further down the road.
1613: It's easy to forget that the heroic Rasmussen is still out there, such is the excitement behind him. He passes under the 3km banner, exactly 1km ahead of Sastre.
1609: Not since Miguel Indurain's legs went to toffee chasing Bjarne Riis in 1996 has a big name in the Tour cracked like Landis has today. Sastre has moved past Leipheimer, whose shoulders are also starting to rock.
1607: Andreas Kloden's T-Mobile team continue to set a brutal pace, in the way Lance Armstrong's Discovery men used to in the mountains. Landis has really cracked as two more riders whiz past him. Sastre has joined Leipheimer in the second group on the road. The CSC rider is 2'07" behind Pereiro in the GC.
1600: Menchov breaks from the T-Mobile group, following Sastre. He may not gain enough time to grab yellow but is grabbing vital time here. Pereiro looks most likely to benefit as he stays in the group and Landis looks in agony.
1558: This could be the key moment of this year's Tour. Carlos Sastre leaps off the front, T-Mobile up the pace to catch him and Landis falls off the back. He's already 15 seconds behind and looks like he's pedalling through tar.
1555: Landis has come up trumps here. With Kloden currently sixth in the general classification, his T-Mobile team are keep to keep him ahead of Leipheimer (who is currently ninth) and are pacing the bunch containing all the main riders, but none of the race leader's Phonak men now.
1552: T-Mobile help Landis close the gap, looking to keep Menchov within their leader Kloden's grasp rather than helping their team-mate Rogers escape.
1550: Now the fun starts on the final climb of the day, with Denis Menchov attacking the Landis group. Michael Rogers and Pereiro - only 10 seconds back in the GC - have gone with him.
1548: Frank Schleck, yesterday's winner, is in the place no one wants to be - the camera's sights at l'arriere du peloton. In other words, he's dropped off the back of the bunch.
1544: With the pressure growing from the bunch, Valjavec appears to have suffered la bonk and Leipheimer has gone it alone.
1541: Rasmussen becomes the first ever Tour rider to climb La Toussuire, which begins 20km from the finish.
1536: The Phonak team of Landis and Oscar Pereiro's Caisse D'Epargne roulers are leading the peloton, trying to keep Leipheimer from opening too much of a gap on their men. Leipheimer started the day 6min 18secs back in the GC and is currently around 2'20" ahead of the peloton.
1520: Almost a disaster for Rasmussen as he runs wide down this tricky and treacherous descent. The riders will have to keep their wits about them if they are to stay on the tarmac.
1514 Another climb, another maximum for Rasmussen. He takes the Col du Mollard to extend his King of the Mountains lead. Valjavec has responded to Leipheimer and the pair are just under five minutes off the lead.
Result of Col du Mollard climb:
1. Rasmussen (RAB) 10pts
2. Leipheimer (GST) 9pts - 4'45"
3. Valjavec (LAM) 8pts - 4'45"
4. Casar (FDJ) 7pts - at 7'00"
5. Zandio (CEI) 6pts - at 7'25"
1507: Leipheimer is looking good and puts on another burst to leave Casar behind. He eventually passes Valjavec to take second place.
1500: Rasmussen begins the category two climb up the Col du Mollard which has an average gradient of 6.8%.
1454: The descent down the Croix-de-Fer is well underway. Rasmussen looks imperious out front with 43km left and is almost five minutes ahead of Valjavec. Casar has done well to stick with Leipheimer and the pair are 54 seconds further back. Moncoutie is still on his own but is only 26 seconds ahead of the 29-strong Groupe Maillot Jaune and two minutes behind Casar and Leipheimer.
1442: Rasmussen goes over the top and takes his second climb of the day to bag another 20 points and claim the King of the Mountains jersey from De la Fuente.
Result of Col de la Croix de Fer climb:
1. Rasmussen (RAB) 20pts
2. Valjavec (LAM) 18pts - 4'55¿
3. Leipheimer (GST) 16pts - 5'31¿
4. Casar (FDJ) 14pts - 5'31¿
5. Moncoutie (COF) 12pts - 7'51
1438: Climbing specialist David Moncoutie of the Cofidis team leaves the Groupe Maillot Jaune to try and catch Leipheimer, who has hunted down a clearly struggling Casar.
1436: Rasmussen is roared on by a massive crowd as he nears the summit. A couple of fans come perilously close to being run over by a support car but get out of the way in time.
1431: There are 59km to go and Rasmussen is 3:23 ahead of Valjavec. He will claim this climb and will be looking for a stage victory as well. Casar is 55 seconds behind the Slovenian while Leipheimer is a further 1:13 back.
1425: Lance Armstrong is seen in the Discovery Channel support car which is trying to find its way up the narrow mountain road. A group of 28 riders, including Landis, Matthias Kessler and Andreas Kloden leave the peloton but are still over seven minutes behind Rasmussen.
1417: With 63 to go, there are only four riders ahead of the peloton. That is leader Rasmussen, Valjavec in second, Casar in third while Levi Leipheimer has tried to breakaway.
1404: Rasmussen is after maximum points for this climb and leaves Valjavec behind to take a 1:20 lead. Casar is now over two minutes off the pace. The peloton, which swallows up Simoni, may be seven minutes behind Rasmussen but the CSC riders at the front up the pace.
1355: Verdugo, Marchante and Garcia Acosta fall off the 14-man chasing group and are now in the peloton. Casar, who was sixth in this year's Giro d'Italia, is now 50 seconds behind the front two.
1345: There is movement at the front as Casar struggles with the slopes of Croix-de-Fer and Valjavec and Rasmussen leave him behind. David Kopp and Steven De Jongh have decided that enough is enough and quit the race.
1342: The leading trio are on the march and are now 6:20 ahead. The 14-man chasing pack have given up the ghost and could soon be caught up by the peloton.
1334: The long descent is now over and the second hors category climb, up the Col de la Croix-de-Fer, begins. Valjavec takes the second and final sprint of the day.
Result of second sprint1. Tajec Valjavec (LAM) 6pts
2. Sandy Casar (FDJ) 4pts
3. Michael Rasmussen (RAB) 2pts
1322: The peloton, which includes Landis, does not seem too bothered by the breakaway and with 97km gone and 85km to go, they are 7:11 off the pace. Popovych's chasing group is almost five minutes behind.
1314: Remember that old TV advert for Cycling Weekly, when the rider hands back his feed bag because it doesn't have his favourite publication in it? There is no handing back of musettes today as the leaders pass the feed station.
1311: McEwen's grip on green tightens as Daniele Bennati (LAM), who was third in the points standing, abandons the race after a crash at the back of the peloton. Tom Boonen, who was second, dropped out yesterday. Oscar Friere looks like Robbie's only real rival now.
1306: Cofidis rider Sylvain Chavenal has taken a tumble on the descent of the Telegraphe, on a piece of road that has a large concrete curbing. He was lying on the road as the TV motorbike arrived, but is now back on his back, although looking woozy.
1304: Some research by the TV company covering the race suggests Andreas Kloden (TMO), who is sixth in the general classification, would be wearing the combined jersey were it still available. Landis has the best combined position in the yellow, green and polka dot jersey standings with Kloden second. Thankfully the garish combined jersey - which had quarters of yellow, green and polka - died a death in the late 1980s.
1259: Green jersey Robbie McEwen isn't likely to be picking up any sprint points at the next opportunity, in St Etienne de Cuines, as he has only just rejoined the peloton following a gruelling climb up the Galibier. The bunch has just crested the Telegraphe.
1253: Valjavex (Lam) is the biggest threat in the lead group as he is just 12min 15sec behind Landis in the general classification and currently 5min 50sec ahead on the road.
1250: Yaroslav Popovych of Discovery has attacked the group of poursuivants and is around 51 second ahead of them. He is still more than two minutes behind the lead trio, though.
1243: There is a small climb up the Col du Telegraphe before a chance for lunch in the town of St Martin de la Porte before the next big business of the day. Valjavec tried to attack the other duo at the front of the race but has been gathered back in.
1233: The tricky Galibier descent claims the first crash of the day. Angel Martin Perdiguero, Christophe Brandt and Manuel Calvente all spill on a left-hand corner but they are quickly back on their bikes.
1230: Rasmussen's maximum reduces David de la Fuente's lead in the King of the Mountains classification. De la Fuente is struggling and did not claim any points on that ascent.
1225: Rasmussen makes a charge for the line and the other two are fully prepared to let him go. The Dane takes the 20 points with Frenchman Casar in second. The climb is over and the speedy descent now begins.
Result of Col du Galibier climb:
1. Rasmussen (RAB) 20pts
2. Casar (FDJ) 18pts
3. Valjavec (LAM) 16pts
1222: There are more and more people at the side of the road which means only one thing, the summit is near. Some decide to run beside the leading trio in a bid to help them along.
1214: There is under 4km to go before the summit. With the legs and lungs burning, the mood of the riders will have been lifted by the sight a colourfully-dressed clown cheering them on by the side of the road.
1204: The chasing group, who are now joined by Verdugo, are now two minutes behind the leaders. The peloton, snaking its way through the mountains, looks to be quite happy where they are and are over four minutes off the pace.
1200: Sad news. Sebastien Joly, the lanterne rouge of the Tour - as the man last in the overall standings - has pulled out and is soon joined by Maxim Iglinski.
1155: Calzati (AG2R), who failed with a bid to leave the peloton a little earlier, finally succeeds. The chasing group is now 14 strong and they are 2min 27sec behind with 33km gone. In the first hour, the riders covered over 32km, not bad considering they are on a severe climb.
1147: The leading trio are still intact and working well together. They are 1min 55sec ahead now. The groups of five and eight have merged and this bunch are 2min 40sec in front of the peloton.
1143: Floyd Landis is proudly wearing his yellow jersey at the head of the peloton with his Phonak team-mates. Landis is the bookies favourite to take the stage but is playing down his chances. He said on Tuesday: "I think that with our conservative tactics, probably the only chance of a stage win is on the time trial. The time difference is not so big yet so I have to be careful."
1141: There is a lot of movement with 16km of the gruelling opening climb to go. Sylvain Calzati, Christophe Rinero and David Moncoutie try to leave the peloton but their efforts are for nothing as they are swallowed up.
1135: The first points of the day are awarded after the riders complete the sprint at the 26.5km mark. Valjavec is over the line first to take the six points.
Result of first sprint:
1. Tajec Valjavec 6pts
2. Sandy Casar 4pts
3. Michael Rasmussen 2pts
1133: A quick summary of how things stand. The leading trio are 1:10 ahead of their closest rivals. The first chasing group are then 45 seconds ahead of Popovych's gang, who are 30 seconds in front of the peloton.
1129: Saunier Duval's Gilberto Simoni is up and working hard to try and catch the eight chasers. He attacks on the 18km mark but gives up the ghost and is caught by four others, Yaroslav Popovych, Patrik Sinkewitz, David Arroyo and Ivan Ramiro Parra to form a five-strong second chasing group.
1124: Bruseghin and Laurent Lefevre make the chasing six an eight and are over minute behind the leaders.
1122: With the peloton seeming to slow the pace a little, hardly surprisingly considering the heat, the leading trio are 1:30 ahead of the peloton.
1117: The five pursuers, Mikel Astarloza, Jose Luis Rubiera, Salvatore Commesso, Vicente Garcia Acosta and Marchante are gaining ground. With 169km to go they swallow up Gorka Verdugo, who had earlier left the peloton.
1110: Sandy Casar of the FDJeux team tries to reel in the leading pair and despite a pained look on his face, manages to catch them. They are now 25 seconds ahead of the peloton, although a group of five are trying to hunt them down.
1102: Lampre's Tadej Valjavec and Michael Rasmussen of the Rabobank team step on the gas on 6km. This breakaway looks to be more successful and they soon establish a 12-second lead.
1057: Christophe Moreau of AG2R decides that he wants to be alone and leaves the peloton. Marzio Bruseghin and Jose Angel Gomez Marchante close him down and eventually the peloton catch up. The breakaway is over after just 1km.
1052: The riders are up off their seats as the peloton starts the climb. They are in for a long, hard day on stage that some regard as the toughest of the Tour.
1047: The flag drops and racing is underway. It is a steady start as the riders enjoy a brief flat stretch. They soon will start the first climb of the day, the hors category Col du Galibier which stands at 2,642m. Just for good measure, the riders have the first of the day's two sprints halfway up.
1045: The riders are in the 2.7km neutral zone and yellow jersey owner Floyd Landis is cheerfully smiling and chatting with his fellow riders. The weather is hot for this brutal stage in the Alps, it is 30C in the air and 37C at road level.