The Olympic anti-doping authority has conceded it may not be able to detect the use of human growth hormone in Beijing.
Hundreds of drug tests have already been performed ahead of the Games opening and during the event 4,500 samples will be collected and tested.
The chairman of the International Olympic Committee's Medical Commission, professor Arne Ljungqvist, recently said developments in tracing substances such as HGH would be introduced at the Beijing Games.
HGH stimulates muscle and tissue growth and is undetectable with standard testing methods.
But the deputy director of the Olympic Anti-doping National Laboratory, Wu Moutian, says it will be hard to catch athletes using the doping method.
However he says he's confident they could detect the blood-booster EPO.
