And now, to the fall from grace for a cycling champion, lance armstrong. The cancer survivor who gave america so much to cheer about. Seven times, he seemed to do the IMPOSSIBLE AT THE TOUR de France, and then, the doping scandal. And now his medals, his glory, his future in question. Here's abc's neal karlinsky. Reporter: In the span of just 24 hours, lance armstrong has gone from champion to disgrace. Headlines around the world were quick to tear into the SEVEN-TIME tour de France winner. The u.S. Anti-doping agency said today, it's official. Armstrong is banned for life and disqualified of all competitive results since august 1998. All of it, they say, because he used prohibited substances including epo, blood transfusions, test tros trone, masking agents. He has been without doubt the finest rider in this race. Reporter: His story is the stuff of legends. He beat cancer. Became the greate eest rider of the world's hardest race and turned his name into a brand. What am I on? I'm on my bike. Reporter: But if he didn't win those seven tours, figuring out who did won't be easy. With the exception of the single man, the top podium positions, 21 riders in seven years, are filled with racers implicated in doping scandals. In nearly every single case, the second, the runner up has had been imply kated in doping at some point. Reporter: Armstrong still maintains his innocence and says in a statement, "enough is enough. Today ill turn the page, I will no longer address this issue. Regardless of the circumstances. His livestrong cancer foundation sold more than 100 million of those famous yellow wristbands and he is estimated to have earned $10 million a year at times during his storied career. Today, nike is sticking with him, though usada says he's no LONGER A tour de France winner. Just another drug cheat who finally got caught. And still all ah ahead on "world news,"