Armstrong's Astana team was dominant in the time trial through the hills and hairpin turns of Monaco, led by the cyclist who would be his heir as Tour titan - Alberto Contador of Spain.

The Texan, who has a record seven Tour victories, is making his return to cycling's showcase event after ending a 31/2-year retirement this winter. The 37-year-old Armstrong, one of the oldest riders in the pack, had a chance to test out his legs and state of mind.

"I was nervous, I was excited and trying to focus on doing the right race specifically in terms of starting easy and finishing good," he said. "When I finished, I was tired - yeah, it was a hard race."

Cancellara took the yellow jersey by finishing the 9.6-mile time trial in 19 minutes, 32 seconds - 18 seconds ahead of Contador, the 2007 Tour winner.

"I didn't expect to win or to take the jersey. I didn't expect a super, super performance," Armstrong said. "It's been a long time since I've had that emotion of being on the start ramp at the Tour."

The race against the clock, in which riders set off one by one, offered an early shakeout about the potential contenders to win the three-week cycling showcase.

Contador showed he was ready.

"Fabian is a great champion . . . [but] my form is very good," the 26-year-old Spaniard said. "I must try to keep up this level. I think I have started well."

Contador was forced to sit out last year because of doping problems at Astana before he joined. He is a far better climber than Cancellara, and the Pyrenees loom in Stage 7.

Contador led four Astana riders into the top 10. Andreas Kloeden of Germany was fourth, American Levi Leipheimer was sixth, and rival Armstrong was 40 seconds back in 10th.

Contador got an edge on other title hopefuls. Two-time Tour runner-up Cadel Evans of Australia was 23 seconds behind Cancellara in fifth, and Giro d'Italia winner Denis Menchov was 1 minute, 31 seconds back in 53d place.

Carlos Sastre, the reigning Tour champion, was 1:06 behind Cancellara.

Tour de France At a Glance

Yesterday: The first stage was a 9.6-mile individual time trial in Monaco.

Winner: Fabian Cancellara of Switzerland earned his fourth stage victory on the Tour. He completed the course in 19 minutes, 32 seconds. The Olympic champion beat 2007 Tour winner and race favorite Alberto Contador of Spain, who took second place 18 seconds behind.

Yellow jersey: Cancellara.

Today: The second stage takes the peloton from Monaco to Brignoles on a 116.2-mile route in an undeveloped region of the Mediterranean. The stage is punctuated by four small climbs.

- Associated Press