Lance Armstrong took the yellow jersey for the first time at this year's Tour de France as his US Postal team dominated Wednesday's team time trial.
The 64.5km stage from Cambrai to Arras was made hazardous by torrential rain which began shortly after the start.
But the US Postal team did not appear to be hindered, clocking one hour 12 minutes and three seconds.
That put them more than one minute ahead of Tyler Hamilton's Phonak team, with Illes Balears in third place.
Jan Ullrich, the man most likely to scupper Armstrong's bid for a record sixth Tour title, was only able to make fourth with his T-Mobile team.
Ullrich's team were more than one minute behind US Postal, although new rules designed to limit the advantage that top teams gain in team time trials meant the German lost 40 seconds in all.
Despite the rain, Armstrong's team clocked an average speed of 53.71 kilometers an hour, the third fastest time in the history of the event.
US Postal now occupy the top five places in the general classification.
"It really was a special day for the team. The team was incredible. The rhythm was perfect," said Armstrong.
"That's the sign of a great team. We fought hard," he said.