Prior to the Olympic competition, several prominent athletes were ruled out of the competition due to failed tests. World indoor medallists Dimitrios Chondrokoukis , Debbie Dunn , and Mariem Alaoui Selsouli were withdrawn from their Olympic teams in July for doping, as was 2004 Olympic medallist Zoltán Kővágó .    At the Olympic competition, Tameka Williams admitted to taking a banned stimulant and was removed from the games.  Ivan Tsikhan did not compete in the hammer throw as a re-test of his sample from the 2004 Athens Olympics , where he won silver, was positive.  Hassan Hirt ,  Amine Laâlou ,  Marina Marghieva ,  Diego Palomeque ,  and defending 50 km walk champion Alex Schwazer were also suspended before taking part in their events. 
Five athletes tested positive for the stimulant bromantan and were disqualified by the IOC, but later reinstated after an appeal to the Court of Arbitration for Sport: swimmers Andrey Korneyev and Nina Zhivanevskaya , Greco-Roman wrestler Zafar Guliyev and sprinter Marina Trandenkova , all from Russia, and the Lithuanian track cyclist Rita Razmaitė . Dr. Vitaly Slionssarenko, physician to the Lithuanian cycling team and team coach Boris Vasilyev were expelled from the games.    The CAS overturned the IOC decision, because bromantan had only recently been added to the prohibited list,  and the athletes and officials were reprimanded.    The Russians had argued that bromantans wasn't a stimulant and thus not banned.