Questioned by the "Tonight Show" host Tuesday, Landis said he may have unknowingly ingested something that made him test positive for a high testosterone ratio.
"I see you on these shows and I do want to believe you and evidence seems — I don't know if it's overwhelming — but it seems pretty conclusive, right?" Leno said.
Landis said yes, if one goes by the tests, and Leno shot back, `Why should we not go by the tests? Tell me why."'
Landis responded that there were several possibilities, saying, "The tests and the people doing the tests would like you to believe that the only possibility is that I essentially took some drugs and that's why the test is that way."
He offered still another new theory: "Now there's also the possibility, and it's an argument that has been used by other people. At this point, I don't know if it's somehow or some way I ingested something that caused the tests to be that way."
Landis went on to repeat some possibilities he and his defense team had floated earlier, that there was some type of natural occurrence in his body that caused the positive tests.
He added, "And I'm beginning to wonder about this myself after the way the situation's been handled, is that after the (sample) leaves my hands ... after I give them the sample, I don't know where it goes."
There wasn't much joking while Landis was on the show, although Leno had said in his monologue, "Tonight we have a man on this show who has way too much testosterone — Bill Maher."
Leno also said that he rode his bike to work because Landis was going to be on the show, grinning and adding, "Oh, yeah. It was my Harley."
Landis himself got a laugh from the studio audience by defending Leno against Maher.
At one point during the exchanges between Leno and Landis, Maher chimed in, "It seems like we're having a giant debate about a sport no one gives a ... about. Does anyone ever watch people bicycle racing, except for the last 10 seconds?"
Landis spoke up, "He has a hard time getting guests here. Leave the guy alone."
The crowd laughed and applauded.
After falling out of first place and back into the pack at this year's Tour de France, Landis came roaring back to win stage 17 in the Alps with one of the more remarkable rides in cycling history.
Both of Landis' "A" and "B" samples taken after that stage turned up a testosterone/epitestosterone ratio of 11:1 — far in excess of the 4:1 limit. Further tests also showed that the samples contained synthetic testosterone, indicating that it was from an outside source.
Landis has maintained his innocence throughout.
He and his defense team initially claimed that any of numerous factors could have led to the high testosterone readings, including cortisone shots taken for pain in his degenerating hip; drinking beer and whiskey the night before; thyroid medication; his natural metabolism; and dehydration, a theory rebuffed by anti-doping experts.
Making the round of TV shows this week, Landis has said his early reaction to the case led people to believe that he was just trying to come up with new excuses.
Tour de France officials no longer consider him the champion, and Landis' Swiss racing team dismissed him. He likely will try to keep his champion's yellow jersey by appealing, a process that could take months.
If he eventually is stripped of the championship, he would be the first rider to lose the title in the race's 103-year history.