Allegations of doping have plagued the Tour de France since the early 1900s, when riders drank alcohol and used substances to dull pain. In the past 50 years, some riders have turned to amphetamines to increase stamina and ignore pain, anabolic steroids to gain muscle and strength, or erythropoietin (EPO) to stimulate red-blood cell production and improve oxygen-carrying capacity.
Since the race's inception in 1903, there have been several notable moments involving doping and the Tour:
2007: The Cofidis team pulled out of the Tour de France after rider Cristian Moreni of Italy failed a doping test and was led away by police at the end of the 16th
stage. Moreni tested positive for testosterone after Stage 11 of the Tour, said Didier Simon, of cycling's world governing body, the UCI.
2007: Alexandre Vinokourov is forced out of this year's Tour, along with all members of the Astana team Tuesday, after he tests positive for a banned blood transfusion. The rider from Kazakhstan, a one-time favorite to win cycling's premier event, was tested after his victory in the Stage 13 time trial. He also won this year's 15th stage, the final stage of the 2005 Tour, and another in 2003, when he finished third overall.
2007: Bjarne Riis confesses to using EPO during his 1996 Tour win. Now head of Team CSC, he decides not to join the team for the start of the race in London on July 7.
2006: Jan Ullrich is forced out on the eve of the Tour after being linked to "Operation Puerto" -- a massive Spanish investigation into a blood-doping scandal at a Madrid clinic that implicates more than 50 riders. After he is fired by the T-Mobile team, Ullrich's DNA sample is matched to one of the blood bags in the scandal. The 1997 Tour winner has retired and denies any wrongdoing.
2006: Italian rider Ivan Basso is also kicked out of the Tour. He receives a two-year doping penalty from his cycling federation in June 2007 and accepts the punishment. The 2005 Tour runner-up has confessed to "attempted doping," but says he never actually went through with it.
2006: Tour de France winner Floyd Landis' team says he tested positive for high levels of testosterone after his Stage 17 win. The American is currently hoping to overturn the U.S. Anti-Doping Agency's 34-0 winning record on arbitration hearings and prove he did not take testosterone on his way to victory. Landis says the French lab which tested his samples made key errors. His 2006 victory is not recognized by organizers.
2005: Spaniard Roberto Heras is banned for two years for testing positive for EPO in the Tour of Spain, which he won.
2004: Codifis team rider Philippe Gaumont tells investigators doping was widespread in the team; French police detain British cyclist David Millar (EPO syringes found in his apartment); Spanish rider Jesus Manzano, dismissed by Team Kelme, claims his team forced him to dope and cover it up.
2002: The wife of Lithuanian rider Raimondas Rumsas is arrested after French police find doping substances in the boot of her car. Edita Rumsas says the stock is for her sick mother. Rumsas, who finishes third in the Tour, denies his wife obtained doping products for him and that he ever took any.
1998: Festina cycling team is expelled in the first week of the Tour de France after a team car is found loaded with performance-enhancing drugs. Flamboyant French rider and seven-time winner
of the King of the Mountains jersey Richard Virenque is part of the Festina squad and later makes a tearful confession to a French court that he had used banned substances and is banned for six months.
1997: Uzbekistan's Dshamolidin Abdushparov becomes the first rider disqualified from the Tour for taking banned substances.
1967: British cyclist Tommy Simpson dies climbing Mont Ventoux after using amphetamines to combat exhaustion.
1924: The Pelissier brothers admit to using chloroform, cocaine, aspirin and "horse ointment" to boost performance.
Information from Reuters and The Associated Press was used in this report.