Transcript for First Look: Bruce Jenner Describes 'Emotional Roller Coaster'
Finally tonight, the Diane sawyer exclusive. The much anticipated interview with Bruce Jenner, and a first look tonight. Here's ABC's Amy robach. Reporter: This is the olympic champion America rooted for. Strength, charisma and unbeatable will. 1976, and that moment he won the olympic gold medal in the decathlon, earning the title world's greatest athlete for that victory nearly 40 years ago. There was the wheaties box, the decades of fame. In recent years, the reality show, with his wife Kris and all those children. That hero to so many, now telling to Diane exclusively a part of his life away from cameras that shaped him. It made me who I am. It's going to be an emotional roller coaster, but I'm going to get through it. Reporter: He's a step-father to four, father of six, and unlike any dad, it's that family he worried about most. Those are the only ones I'm concerned with. I can't let myself hurt them. Reporter: The man we once rooted for at the olympics now looks to the future. I want to know how this story ends. You know? How does my story end? Our thanks to Amy. And Diane's entire interview hair airs tomorrow night at 9:00 eastern on ABC. I'll see you tomorrow night.
This transcript has been automatically generated and may not be 100% accurate.