The protest came a day after star rider Alexandre Vinokourov and his Astana team were sent home after he tested positive for a banned blood transfusion.

Today, the pack of riders split into two groups: those who took the start as normal — including controversial race leader Michael Rasmussen — and those who protested by hanging back for a few minutes.

Many of the riders involved in the symbolic protest were from French teams that have long complained that doping is ruining the sport. They simply let Rasmussen, star sprinter Tom Boonen and others ride away — but caught up with them further down the road.

The Tour's Web site said German squad Gerolsteiner also took part in the protest. Some of the French teams involved included Credit Agricole, Cofidis, FDJeux, Bouygues Telecom and Agritubel.

"We're fed up," French rider Ludovic Turpin told Eurosport television.

Fans booed Rasmussen at the start. The Dane is under a cloud of suspicion because he skipped doping tests before the Tour began.

The protest contributed to a 13-minute delay to the scheduled start time of today's stage, the last in the Pyrenees. The race ends Sunday.

Tour organizers announced that 14 riders were subjected to blood tests early today. They were from French teams Cofidis and AG2R. The tests were all negative.

In all, 225 blood tests have been conducted so far at the three-week race. Of those, just one — for Vinokourov — was positive.

Without the Kazakh and his Astana team, the field was reduced to 151 riders today. Astana's withdrawal also meant two of the top 10 riders were out — Andreas Kloeden of Germany, who had been fifth, and Kazakh Andrey Kashechkin, who had been eighth.

Today's 135.8-mile 16th stage from Orthez to Gourette-Col d'Aubisque featured four huge climbs, culminating with an uphill finish so tough it does not even have a rating.

Vinokourov tested positive for a blood transfusion after he won last Saturday's time trial. On Monday, Vinokourov also won stage 15 — a tough climb in the Pyrenees. Those performances marked a remarkable recovery from a crash that had ruined the first week of his race, leaving him with stitches in both knees.

Vinokourov told the French sports daily L'Equipe for today's edition that he had not cheated.

"It's a mistake. I never doped, that's not the way I see my profession," the newspaper quoted him as saying. "I think it's a mistake in part due to my crash. I have spoken to the team doctors who had a hypothesis that there was an enormous amount of blood in my thighs, which could have led to my positive test."

Vinokourov claimed to be the victim of a "provocation."

"It's been going on for months and today they're managing to demolish me," he said. "The setting up of our team made a lot of people jealous and now we're paying the price. It's a shame to leave the Tour this way, but I don't want to waste time in proving my innocence."

Vinokourov did manage a joke about his situation.