Tonight, allegations against one of the most well known and richest yoga gurus on Earth. He's the founder of bikram yoga he claims are revolutionize their well being, your health and your sex life.... See More
Tonight, allegations against one of the most well known and richest yoga gurus on Earth. He's the founder of bikram yoga he claims are revolutionize their well being, your health and your sex life. Now he stands accused of sexually assaulting five of his own foe lers, women who say they believed in him, revered him. "Nightline" has been investigating these allegations for more than a year. And here's David Wright with our report "Yoga guru under fire." Nobody has the right to my body. Reporter: Sarah, a young mother in San Francisco says she can barely bring herself to do the things she loves most. Practicing yoga. One day my daughter looked at me, she was almost 3, and she said to me, mommy, I want to be just like you. I want to be a yoga teacher. And all I can think is you can't do that, you'll get raped. Reporter: This is the man she accuses of assaulting her. Arguably the richest most successful guru in the world. In the yoga world, he's a rock star. Known by just one name -- bikram. His brand of ottawa yoga synonymous with sweat. He claims it can improve your body, prolong your life and invigorate your sex life. The hardest problem in my life is stay away from women. Women like me. I have to run city after city, country after country all my life to stay away from the women. Women like you too much? Yeah. That was a near and a half ago when we started reporting on bikram. Already then there were rumors about inappropriate contact with students. I asked him about those rumors. Every women loves me. You know, presidents daughter, you know, prime minister daughter, you know, billionaire daughter. Superstar, actors, singers. But yogi supposed to be yogi. They cannot involve with the women. Reporter: But since then, five women have filed civil lawsuits accusing him of sexual assault. Four accuse him of rape. Sarah was the first to come forward. She first told her story to "Vanity fair." He absolutely chases women. He victimizes women. And someone can look him in the eye and say no and it doesn't matter. Reporter: She was 20 when she dropped out of college to attend bikram's teacher training program. The gruelling nine-week seminar, led by bikram himself costs thousands of dollars and is the only way to become a bikram yoga teacher. It was a big commitment for me to make this decision. But it was something that I was extremely dedicated and passionate about. Reporter: Meeting bikram for the first time, she say, she was full of hope. She told him his yoga had changed her life. I told him I was sad, now I'm happy. I feel like a completely first person. Bikram, I love you more than chocolate. Reporter: She said he took an immediate interest. He took me by the arms and told me that there was a connection between the two of us that he had never felt before. . Later she says bikram told her privately they should start a relationship. Shaken, she rebuffed H him and reported the incident to a teacher training staffer. He said, he may not be a very good man, but he's a very good teacher. Reporter: Did that seem like good advice? I wasn't really sure what I could do. Reporter: But she says bikram persisted with unwanted advances during class. And he put his hand on my leg and my arm and pulled them apart. Reporter: Your legs at this point are spread and leaning into you from behind? He started whispering things in my ear that nobody else could hear. Don't you love me. Come to L.A. Come be with me. And he displayed me in front of everybody. And it was so humiliating. Reporter: To the outside the teaching can seem unorthodox. Students, almost naked and dripping with sweat are cheered on by bikram's sexually charged banter. I 22 times in one night in seven hours. He's the guru. He's the spiritual master. Reporter: Marissa Anderson said she was one of a select few teachers to become Bart of bikram's entourage. Reporter: I think the guru thing is hard to get. It's not that he's just a really good spin instructor. To you he was something spiritual? Yes. The young women who want to believe in something so badly, he sees it. And those are the people that he targets because they're vulnerable. Reporter: Marissa Anderson said she was vulnerable, recovering from drug addiction. Yoga, she says, was her path to a healthier life. He could walk on water as far as you were concerned? Absolutely. Absolutely. Reporter: She says all that changed late one night at bikram's Beverly hills mansion. He raped me. We were watching he mu view and he grabbed the back of my head and he kissed me. I pulled away and said I don't -- this isn't -- I felt speechless. Because this was my guru. And I thought of him as a father figure. And he stood up and he grabbed my hand and he sat me down on the couch. Then he pulled up my skirt, pulled down my underwear. Pulled his boxer shorts down and had sex with me. And I had said no. Reporter: He raped you there. Yes. Reporter: In his own house? Yes. Reporter: His wife sleeping upstairs. Correct. Reporter: His daughter sleeping upstairs. And his son. It didn't last very long. He didn't use protection. He stood up, put his shorts back on and went back into the other room, sat down on the couch like nothing happened. Reporter: She did not report the alleged incident to the police until years later, but said the rape took place in the very room where bikram and I had sat down for our sbrier. Interview. I never lie, never cheat. Never hurt another human being. I'm the most spiritual man you'll ever meet in your life. Bonn graduated from teacher training and started participating in yoga competitions and she said eventually felt comfortable enough to visit bikram's house, at her coach's urging to get feedback on her routine suddenly you were alone with him at his R his snous. Yes. And he put his happennd inside my leg and his other hand on my breast. And he kept trying to touch me. And he was on top of my body. And he said my wife is a bitch and I need someone to love me. To be with me. To massage me. And then he said to have sex with me. And I said I will never do that. Then he told me that the only way that I could ever win the yoga competition was if I had sex with him. Reporter: He said quid pro quo. Straightforward. You will never win the yoga competition. I pushed him off of me completely. I stood up. I looked him in the eye and said I don't need you to win. I'm going to do it on my own. And I walked out of his house. Reporter: More determined than ever, Bonn did compete. This is her routine. It's run by usa yoga, an organization founded by bikram's wife. Bonn believed the routine was nearly perfect. She placed second. It's wrong. No one, this case aside, no one, no one is entitled to anyone's body. Not ever. And nobody said anything. They just sat there and they let him do it. Reporter: The legal team declined to be interviewed for this story, but the legal team provided this statement. They strongly dispute the allegations and intend to vindicate themselves in court. Adding they do not intend to try this case in the media. He's a sick man. And I'm not even the worst. I got away. Jimmy: When Reporter: When we come back, why the police weren't involved and why is this woman now coming forward. I'm ready because it's my truth. Truth that I want people to know. Reporter: And more from bikram who for years has scoffed at his critics including this when we spoke to him a year ago. People get jealous. People talk bad about Jesus also. So what?
This transcript has been automatically generated and may not be 100% accurate.