But, reports CBS News Correspondent Richard Roth, the cycling champion is fighting back in public.
With his reputation as the world's most celebrated athlete challenged, Armstrongthat a performance-enhancing drug may have helped him achieve the first of his seven Tour de France victories, in 1999.
He says he's the target of a "setup" and, on CNN's "Larry King Live," questioned the credibility of the French laboratory that released results of his urine tests, saying, "Do you think I'm going to trust some guy in a French lab to open my samples and say they're positive and announce that to the world, and not give me the chance to defend myself? That's ludicrous."
According to the French paper L'Equipe, recent tests showed there was a drug called EPO, which boosts endurance, in Armstrong's 1999 samples. At the time, there was no test for EPO, which Armstrong says he did use as a cancer patient, years before he became a Tour de France competitor.
Armstrong denies he's ever used drugs to boost his performance in his sport: "I've said it for seven years. I've said it for longer than seven years. I have never doped. I can say it again. But I've said it for seven years. It doesn't help. But the fact of the matter is, I haven't."
It may be an allegation that'll never be resolved.
Asked if he's considering a lawsuit, Armstrong said that "just keeps a bad story alive ... forever."