Tonight, the secret Bruce Jenner says he always tried to keep hidden now coming to light. The olympic legend, turned reality show patriarch had the world hanging on his every word as he sat down with... See More
Tonight, the secret Bruce Jenner says he always tried to keep hidden now coming to light. The olympic legend, turned reality show patriarch had the world hanging on his every word as he sat down with our own Diane sawyer for that intimate anticipated interview revealing he considers himself a woman. We want to begin with a note about pro nouns. In this he said we should use a familiar pro-noun for him as we try to tell his story. How are you doing? Reporter: He is 6'2", welcoming and apprehensive. It's going to be an emotional roller coaster but somehow will get through it. Come in to my house. As we sit down the person's whose face has changed so much over recent years is quiet. Knowing the moment that carries you forward can also mean no way back. So Bruce Jenner is -- Bruce Jenner is -- um, I would say I have always been confused with my gender identity since I was this big. I look at it this way, Bruce always telling a lie, lived a lie his whole life about who he is. I can't do that any longer. So when I take my pony tail out when we talk about this stuff. Let's take the pole pony tail out. A symbolic moment after 65 years. In a sense, we start again. Are you a woman? Um, yes. For all intents and purposes, I am a woman. People look at me differently. They see you as this macho male but my heart and soul and everything that I do in life it is part of me. That female side is part of me. That's who I am. I was not genetically born that way. I have all of the male parts and all of that kind of stuff. So a lot of ways we are different, okay, but we still identify as female. That's very hard for Bruce Jenner to say. Because why? I don't want to disappoint people. ? Reporter: Hundreds of millions of people who once cheered a real-life American super hero. ? the olympics, 1976, he has just been proclaimed the greatest athlete in the world. You were the world's greatest athlete. Uh-huh. Reporter: We see -- what do you see. A confused person running away from my life and who I was. Reporter: With fear? Bl big-time fear, scared to death. Didn't know what my future held at that time. Reporter: Everybody struggling with what this is. That is me. That is her. Reporter: People have to know that you can want to identify as a woman and still -- Kick butt. Reporter: Since a small boy he has a growing certainty that for some reason the gender of his body is different from the gender he feels in his soul. I look at guys and I go, he's comfortable in his own skin. You know? I thought wouldn't that be a nice way to go through life. I look at women all the time thinking, oh, my god, how lucky are they can wake up in the morning and be themselves. But me, I'm stuck here in the middle. I got nowhere to go, which way do I go? Reporter: For the next 40 years wrestling an inner torment, through marriages to the women he loved, raising children he could not bear to hurt, and finally as an collusive character on that reality show in which every private thing in life seemed ready to be bartered for fame. We told him there was a lot of skepticism among people watching him tonight. People are convinced that this is a stunt to promote the show. Yeah, we're doing this for publicity. Yeah, right. Oh, god, Diane, do you have any idea what I have been going through all of my life and they are saying we are going to do this for publicity for a show. There's a lot of shows out there. Reporter: No but they think -- I understand where you are coming from. Reporter: There is a shameless selling of everything these days. I know. And I get that. But what I'm doing is going to do some good. And we're going to change the world. I really firmly believe that. That we're going to make a difference in the world with what we are doing. Reporter: He says his story tonight is just one of so many. An estimated 700,000 transgender Americans all around us. I want to change. Reporter: People of powerful talent and vulnerability, suicide, murder, discrimination. This is so hard. Reporter: Homelessness. I'm transgender. Reporter: Ridiculed. I'm excited to start my life as a single middle-aged woman, says Bruce. Reporter: He says he can't speak for them but he hopes his decision to come forward will help. His dream re-emerge as the person he calls her. Bruce lives a lie. She is not a lie. I can't do it anymore. Reporter: But you understand that people are baffled, confounded. Apart from the people who are just, oh, my god. Is he gay. Are you gay? No. I'm not gay. I'm as far as I know heterosexual. Reporter: What do you mean as far as you know? I have never been with a guy. I have always been married, raising kids. Reporter: You can desire a woman every bit as much? Yeah. Reporter: He is almost amused by my attempt to walk through this maze. It's the confusion inside of this. So much confusion. Reporter: If you were male and you become female, but you like women, are you a lesbian? Are you a heterosexual who -- Going back to the sex thing and it is apples and Oranges. There are two different things here. Sexuality is who you are personally attracted to, who turns you on, male or female, but gender identity is how to do it with who you are as a person and your soul and who you identify with inside. Reporter: Were you as fair to the women you married. Not as fair as I should have been. Reporter: When you look back and say I apologize for that. I have apologized to everybody. I have done nothing but apologize for my entire life. Reporter: He was fighting the problem but falling apart. He's approaching 40. Divorced for the second time, his income falling off. He's fighting depression. With the help of a therapist he makes a big decision to stop trying to run away. He begins transitioning in to a woman. A doctor prescribes female hormones, estrogen and he says right away the intense daily feelings of fear and frustration subside. And remember, this is back in the '80s, 30 years ago. God, I started on hormones. Reporter: In the '80s you started? Oh, yeah. Reporter: How much did you do? How long did you do it? Almost five years. Reporter: He starts to change his face, getting surgery on his nose and electrolysis to remove his beard and hair on his chest but when he is transitioning in to a woman he says something stopped him. He simply lost his nerve. He looked at his little children and couldn't bear to cause them pain. Those are the only ones I'm concerned with and the only ones in my life they don't -- I can't allow -- I can't let myself hurt them.
This transcript has been automatically generated and may not be 100% accurate.