Athletes accused of using banned substances threaten the integrity of sports ranging from track and field to baseball and cycling. Will the NFL be next? Here is a look at key moments in the evolution of sports doping.
• September 1988: Speed demon Ben Johnson is stripped of Olympic gold for testing positive for a banned steroid after winning the 100-meter race.
• November 1999: World Anti-Doping Agency is established to coordinate and monitor the fight against doping in sports.
• September 2003: Federal authorities raid BALCO, a California company suspected of supplying illegal performance-enhancing drugs to professional and Olympic athletes. The BALCO scandal would eventually reveal that doping in sports is endemic.
• December 2004: Giants slugger Barry Bonds is reported to have testified to a grand jury in late 2003, per the BALCO case, that he used steroids during the 2003 season, but unwittingly. Three years later, he would be charged with perjury and obstruction of justice.
• March 2005: Major League Baseball's Mark McGwire sidesteps questions about his own steroid use during testimony on Capitol Hill, as lawmakers threaten federal legislation to govern drug testing in baseball. Five years later he would admit to using steroids.