In it, he says he used steroids on and off during his career, including during the great home run chase of 1998.
In addition to the statement, McGwire spoke on the telephone with the AP, which reports McGwire's voice cracked repeatedly during the 20-minute interview.
"It's very emotional, it's telling family members, friends and coaches, you know, it's former teammates to try to get a hold of, you know, that I'm coming clean and being honest," he said. "It's the first time they've ever heard me, you know, talk about this. I hid it from everybody."
McGwire said now is the time to go public, since he has re-emerged on the baseball scene as a hitting coach for the St. Louis Cardinals.
Cardinals manager Tony La Russa, who has long been McGwire's biggest supporter, said he didn't know McGwire used steroids until McGwire called him Monday and told him.
"I'm really encouraged that he would step forward," La Russa told ESPN. "As we go along his explanations will be well received."
He also called MLB commissioner Bud Selig to apologize. In a statement, Selig said he is happy with McGwire's current actions:
"I am pleased that Mark McGwire has confronted his use of performance-enhancing substances as a player. Being truthful is always the correct course of action, which is why I had commissioned Senator George Mitchell to conduct his investigation. This statement of contrition, I believe, will make Mark's re-entry into the game much smoother and easier."
McGwire left the public stage in 2005 after his infamous testimony before Congress, in which he repeatedly said "I'm not here to talk about the past" in response to his alleged steroid use. He now says he wanted to tell the truth, but his lawyers advised him against it.
"That was the worst 48 hours of my life," McGwire now says.
Here is the entire statement:
"Now that I have become the hitting coach for the St. Louis Cardinals, I have the chance to do something that I wish I was able to do five years ago.
I never knew when, but I always knew this day would come. It's time for me to talk about the past and to confirm what people have suspected. I used steroids during my playing career and I apologize. I remember trying steroids very briefly in the 1989/1990 off season and then after I was injured in 1993, I used steroids again. I used them on occasion throughout the '90s, including during the 1998 season.
I wish I had never touched steroids. It was foolish and it was a mistake. I truly apologize. Looking back, I wish I had never played during the steroid era.
During the mid-'90s, I went on the DL seven times and missed 228 games over five years. I experienced a lot of injuries, including a ribcage strain, a torn left heel muscle, a stress fracture of the left heel, and a torn right heel muscle. It was definitely a miserable bunch of years and I told myself that steroids could help me recover faster. I thought they would help me heal and prevent injuries, too.
I'm sure people will wonder if I could have hit all those home runs had I never taken steroids. I had good years when I didn't take any and I had bad years when I didn't take any. I had good years when I took steroids and I had bad years when I took steroids. But no matter what, I shouldn't have done it and for that I'm truly sorry.
Baseball is really different now -- it's been cleaned up. The commissioner and the players' association implemented testing and they cracked down, and I'm glad they did.
I'm grateful to the Cardinals for bringing me back to baseball. I want to say thank you to Cardinals owner Mr. DeWitt, to my GM, John Mozeliak, and to my manager, Tony La Russa. I can't wait to put the uniform on again and to be back on the field in front of the great fans in Saint Louis. I've always appreciated their support and I intend to earn it again, this time as hitting coach. I'm going to pour myself into this job and do everything I can to help the Cardinals hitters become the best players for years to come.
After all this time, I want to come clean. I was not in a position to do that five years ago in my congressional testimony, but now I feel an obligation to discuss this and to answer questions about it. I'll do that, and then I just want to help my team."