The World Anti-Doping Authority says any athletes planning to cheat in Beijing are more likely to get caught than ever before.
WADA president John Faye says they're smarter than they used to be and initiatives such as target testing based on intelligence means it will be harder for athletes to get away with doping.
The Russian Olympic team has denied accusations of systematic doping among its athletes after seven female athletes were expelled or suspended from the Games in the past week.
Faye says there's no reason to believe there is systematic doping going on anywhere.
Russia has questioned the timing of the announcements of the suspensions just days before the Olympics.
While the head of Russia's athletics federation says doping is "a sporting crime" a Russian Olympic Committee spokesman says talk of systematic doping is premature and intended to create unpleasantness.
He says when the Balco laboratories was found in California no one said the whole of US sport was involved in doping.