Hamilton to quit

Miami - Olympic gold medalist Tyler Hamilton has tested positive for a banned substance and is retiring from cycling.

Hamilton said on Friday that his positive test stemmed from use of an over-the-counter antidepressant.

Hamilton told The Associated Press "there's nothing to fight about." He says he took a banned substance and accepts the consequences.

Tyler won gold at the Athens Games, but that success was overshadowed by a blood-doping scandal. He served a two-year doping suspension that ended in 2007.

The new positive test - which the US Anti-Doping Agency hasn't revealed - could bring a ban of eight years or more, essentially ending the career of the 38-year-old cyclist.