Looking nervous and periodically swallowing hard, Armstrong said that he used testosterone, cortisone, human growth hormone and the blood booster EPO, but that he was never the ringleader of the doping program on his Tour de France-winning teams or used any drugs that other riders were not doing at the time.
He called his doping regimen simple and conservative, rebutting the claim by the U.S. Anti-Doping Agency that the drug program on his Tour de France-winning teams was "the most sophisticated, organized and professionalized" doping scheme in the history of sports.
Armstrong remained dry-eyed throughout the 90-minute program. The second part of the interview will be broadcast on Friday on Winfrey's network, OWN.
He apologized to several people, including the former masseuse Emma O'Reilly, one of the people he tried to crush when they claimed he had doped.
He called his quickness to fight "a major flaw" and said he was "a guy who expected to get what he wanted and to control every outcome - it's inexcusable."
"There will be people who hear this and never forgive me," he said. "I understand that."
He also said he had been a bully his whole life, before contradicting himself a minute later, saying he became a bully only after he resumed his cycling career following a fight with cancer.
And when he said he never failed a drug test - saying, "I passed them because there was nothing in the system" - he contradicted himself again.
When Winfrey asked if his urine samples from the 1999 Tour retroactively tested positive for EPO, he said yes. When she pressed him about O'Reilly's claim that Armstrong received a backdated prescription from a team doctor after he tested positive for cortisone at the 1999 Tour, he also said yes. (Watch the interview here)
What he did not do was delve into the details of his doping, never explaining how it was done or who helped him do it. He said he was not comfortable talking about other people when asked about the infamous Italian sports doctor Michele Ferrari, his former trainer who is now serving a lifetime ban for doping.
When Winfrey asked if he would cooperate with the U.S. Anti-Doping Agency in building doping cases against others in the sport, he masterfully skirted the question.
But it did not really matter what Armstrong told Winfrey in the interview, at least according to anti-doping officials who hold the key to Armstrong's future as a professional athlete.
Armstrong's reason for coming clean was not to unburden himself of the deception he fought to keep secret for so long. It was to take the first step toward mitigating the lifetime ban from Olympic sports that he received from USADA last fall, according to people close to him who did not want their names published because they wanted to stay in Armstrong's good graces.
Anti-doping officials need to hear more from Armstrong than just an apology and a rough outline of his doping. They need details. And lots of them.
"Anything he says on TV would have no impact whatsoever under the rules on his lifetime suspension," said Travis Tygart, the chief executive of the USADA.
Armstrong, 41, wants to compete in triathlons and in running events again, but is barred from many of those events because they are sanctioned by organizations that follow the World Anti-Doping Code. To get back into those events, he must tell anti-doping officials who helped him dope, who knew about his doping and who helped him perpetuate one of the biggest cover-ups in the history of sports.
In digging up those details, Armstrong might be able to dig himself out of his lifetime ban in exchange for a reduced ban of, perhaps, eight years.
It might also shine the spotlight on some of the most powerful men in the sport of cycling, including Pat McQuaid, the president of the International Cycling Union and current member of the International Olympic Committee, and Hein Verbruggen, a past president of the cycling union and current honorary member of the IOC.
At least two of Armstrong's teammates have claimed that the cycling union had accepted a bribe from Armstrong to cover-up at least one positive test. But only a small group of people would be able to prove those claims are true, and Armstrong is one of those people.
With Winfrey, Armstrong denied that he had bribed sports officials to hide an alleged positive EPO test at the Tour of Switzerland.
In the end, though, Armstrong seemed to understand that his actions and lies were not normal, even in a sport that was rife with doping during the time he dominated it.
Winfrey asked him if he ever felt his doping was wrong, and he answered no, then added that he realized that was scary.
When she asked him if he had ever felt bad about his doping, he said no, then said, "Even scarier."
Winfrey then asked, "Did you feel in any way that you were cheating?" He said, no, "That's the scariest," and went on to explain that he had even looked up the word cheat in the dictionary once to find out the exact meaning. He found it to be, "gaining an advantage on a rival or foe," and convinced himself that he was not cheating because he considered cycling to be a level playing field back then, with all the top riders using drugs.
"I will spend the rest of my life trying to earn back trust and apologize to people for the rest of my life," he said.