Pau - French time trial champion Sylvain Chavanel abandoned the Tour de France early on the 15th stage from Samatan to Pau on Monday, race organisers announced.
Chavanel, of the Omega-Pharma team, has been sick with a chest infection in recent days and had been taking antibiotics.
His team sports director Brian Holm said: "He's lost his voice and he'd been finding it hard to breathe.
"This morning he was really sick. He spoke with the doctors of the team and they've advised him it would be best to pull out of the Tour."
Chavanel started the 158.5km ride from Samatan to Pau but the frantic pace prompted by several early attacks soon left him trailing.
The Frenchman is now expected to recover as quickly as possible for the Olympic road race which takes place six days after the end of the Tour, on July 28.