an act of personal courage, making history and creating a giant reaction in the iron-clad world of professional sports. One of their own, jason collins,a power house player in the nba, a veteran of... See More
an act of personal courage, making history and creating a giant reaction in the iron-clad world of professional sports. One of their own, jason collins,a power house player in the nba, a veteran of the court, today told the world he is gay. A revelation that makes him the first active player to come out, speak up, and take a stand. So what will happen next? Abc's dan harris starts us off. Reporter: All those worn-out stereotypes about gay men? Jason collins utterly demolishes them. He's a 7-foot, 255-pound, trash-talking bruiser, who has played on six teams over twelve years in the nba, making it to the playoffs nine times. I pride myself on setting tough picks. You know, going out there and being physical. Reporter: Collins made history in "sports illustrated" with these 12 words -- "i'm 34-year-old nba center. I'm black. And I'm gay." Jackie robinson what he was to integration, and billy jean king has been to women's rights and now jason collins for gay rights, I think this is not just big sports news this is big news in our country. Reporter: Collins has been hiding his sexuality for years. Quote, when I was younger, i dated women. I even got engaged. I thought I had to live a certain way -- I kept telling myself the sky was red, but i always knew it was blue. Hgs one small secret gesture of solidarity with the lgbt, wearing the unusually high number 98, a reference to another watershed moment, 1998, the year a young gay man, named matthew shepherd was kidnapped and murdered in wiig. Collins said he knew he had to come out after his roommate told him he marched in bostonas gay pride parade. He felt jealous and ashamed. I want to do the right thing and not hide anymore. I want to take a stand and say, me too. Reporter: Today, reaction from around the league swift and mostly supportive with collins twin brother jarron, who's straight, tweeting - - very proud of you. Reporter: And kobe bryant tweeting -- don't suffocate who u r because of the ignorance of others. He's always been a great guy. He's always been a great teammate. He's no different than anybody else. The guy is happy, whatever he does, that's cool with me. Late today we heard president obama called collins to express his support. He said for years he had trouble sleeping because he was keeping this secret. The day afterly told his story, he says he slept like a baby. And this june he will be marching in the gay pride parade in boston. This is history waiting to be made. Tomorrow he'll sit with an exclusive interview first thing
This transcript has been automatically generated and may not be 100% accurate.