The cyclists on trial are Britain's David Millar's, Italy's Massimiliano Lelli, France's Philippe Gaumont, Robert Sassone and Mederic Clain plus Poland's Marek Rutkiewicz and Daniel Majewski.
The Cofidis team's former physiotherapist, a pharmacist and a sports director are also being tried.
Most are charged with acquiring and possessing banned performance-enhancing drugs, and could face up to five years in prison and fines of up to 75,000 euros.
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The trial, expected to last a week in the Paris suburb of Nanterre, follows one of the biggest judicial investigations into the use of banned drugs in the sport.
Defence lawyers have called into question the role of the French Cycling Federation, which is one of the plaintiffs and is demanding 200,000 euros of damages, saying it did nothing to end the violations.
The federation's legal adviser hit back, saying: "People should try to clean up their own house before making accusations."
Millar's lawyer Julien Andreez said: "We are confident that his statements from the beginning have been the same. He has admitted all the facts that he was accused for so he is completely serene and ready to explain himself once again.
"We know what those facts are - he ingested certain substances in Italy, Spain and England and he will repeat those facts again."
Millar was banned for two years and stripped of his gold medal from the 2003 world championship time trial after he admitted taking EPO in 2001 and 2003. He also won the Tour de France's prologue in July 2000.
Millar returned to competition in June after serving the two-year ban and has vowed to become the standard-bearer for clean cycling.
The scandal prompted the French Sports Ministry and the International Cycling Union to adopt new measures to fight doping in cycling and intensify random testing after it became clear riders were often warned before checks.
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