In a 60 Minutes interview airing Sunday, former cycling teammate Tyler Hamilton claims that he witnessed the seven-time Tour De France champ using the performance enhancing drug EPO while prepping for the race in 1999, 2000 and 2001.
For his part, Armstrong, 39, took to Twitter to refute the charges. "20+ year career. 500 drug controls worldwide, in and out of competition. Never a failed test. I rest my case," he tweeted Thursday, May 19.