With just weeks to go before the start of the Olympic Games in Bejing, new doubts are being raised about one of the main drug tests being used to catch athletes who cheat.
Expert scientists in the field say the testing procedure for EPO is flawed, and that it enables athletes to use the blood-boosting medication undetected.
One eminent scientist, Dr Rasmus Damsgaard, says many of the finalists in Olympic endurance events will be using EPO.
He says the problem lies in the definition of a positive test result, as the procedure itself is excellent and is more than capable of detecting the presence of EPO.
But Dr Damsgaard says the criteria for deeming a sample positive are so narrow that almost every athlete taking an odd or uncertified EPO will escape.