World Anti-Doping Agency President John Fahey says more than 100 athletes have been kept out of the London Olympics because of doping.
Fahey says that through mid-June at least 107 athletes drew doping bans, ruling them out of the games.
He adds that not all would have qualified to compete in London.
"I am pleased to say that they are not with us," he said.
Fahey told IOC members that intelligence was shared by WADA, sports federations and London organisers to target athletes under suspicion.
Fahey said athletes who dope should know that "their chances of avoiding detection are the smallest they have ever been".