Ending more than a decade of denials and evasion, McGwire admitted Monday that steroids and human growth hormone helped make him a home run king.
"The toughest thing is my wife, my parents, close friends have had no idea that I hid it from them all this time," he told The Associated Press in an emotional, 20-minute interview. "I knew this day was going to come. I didn't know when."
In a quavering voice, McGwire apologized and said he used steroids and human growth hormone on and off for a decade, starting before the 1990 season and including the year he broke Roger Maris' single-season home run record in 1998.
"I wish I had never touched steroids," McGwire said. "It was foolish and it was a mistake."
He had mostly disappeared since his infamous testimony before a congressional committee in March 2005, when he repeatedly said, "I'm not here to talk about the past," a response that made him an object of ridicule during his self-imposed exile.
Once he was hired by the Cardinals in October to be their hitting coach, however, he knew he had to say something before the start of spring training in mid-February.
"He knows he owes the baseball world an explanation," said former Rep. Tom Davis, the Virginia Republican who chaired the hearing. "I don't think anybody's surprised by this. He was one of hundreds of players who used steroids during this time. ... This was so widespread. Had we not held these hearings and put the fear of God into baseball, it would still be going on."
Before a carefully rolled out schedule of statements and interviews, McGwire called commissioner Bud Selig, St. Louis manager Tony La Russa and Maris' widow, Pat, on Monday to personally break the news.
He started by issuing a statement and calling the AP.
"It was a wrong thing what I did. I totally regret it. I just wish I was never in that era," he said.
McGwire even understands why the Maris family now believes that Maris' 61 homers in 1961 should be considered the authentic record.
"They have every right to," McGwire said in an interview on the MLB Network.
In his AP interview, McGwire's voice shook when he recounted breaking the news to his son, Matt, who is 22. When McGwire hit the record homer, he hoisted Matt — then a 10-year-old batboy — at home plate. The former player called that conversation the toughest task in the ordeal.
"The biggest thing that they said is they're very proud of me, that I'm doing this," he said. "They all believe it's for the better."
While McGwire admitted conduct many had assumed, it marked a huge fall for a player considered one of the greats a decade ago.
"I admire him for doing it. I'm sure it wasn't easy," Cincinnati manager Dusty Baker said. "Maybe he's clearing his conscience."
McGwire was a baseball icon — Big Mac, with a Paul Bunyan physique and a home run swing that made fans come out to the ballpark early to watch batting practice. He hit 583 home runs, tied for eighth on the career list, and his average of one every 10.6 at-bats is the best ever.
His record of 70 home runs in 1998 was surpassed by Barry Bonds' 73 homers in 2001 — the year of McGwire's retirement and the apex of the Steroids Era. Bonds himself has denied knowingly using illegal drugs but has been indicted on charges he made false statements to a federal grand jury and obstructed justice.
In four appearances on the Hall of Fame ballot, McGwire has hovered at 21-24 percent, well below the 75 percent necessary.
"This has nothing to do with the Hall of Fame," he said. "This has to do with me coming clean, getting it off my chest, and five years that I've held this in."
Yet, he sounded as if all the criticism had wounded the pride he had built as the 1987 AL Rookie of the Year and a 12-time All-Star.
"There's no way a pill or an injection will give you hand-eye coordination or the ability or the great mind that I've had as a baseball player," he said.
Hank Aaron, baseball's former career home run champion, responded with a conciliatory tone.
"He has my forgiveness," Aaron told USA Today "If that's all that stands in the way between him being inducted into Cooperstown, we should all forgive him."
McGwire said he first used steroids between the 1989 and 1990 seasons, after helping the Oakland Athletics to a World Series sweep when he and Jose Canseco formed the Bash Brothers. He returned to steroids after the 1993 season, when he missed all but 27 games with a mysterious heel injury, after being told steroids might speed his recovery.
"I did this for health purposes. There's no way I did this for any type of strength purposes," he said.
After being confronted by the AP during the home run streak in 1998, McGwire admitted using androstenedione, a steroid precursor that was then legally available and didn't become a controlled substance until 2004. Baseball and its players didn't agree to ban steroids until a year after his retirement.
McGwire's 70 homers in 1998 came in a compelling race with Sammy Sosa, who finished with 66. More than anything else, the home run spree revitalized baseball following the crippling strike that wiped out the 1994 World Series.
Commissioner Bud Selig praised McGwire, saying, "This statement of contrition, I believe, will make Mark's re-entry into the game much smoother and easier."
McGwire became the second major baseball star in less than a year to admit using illegal steroids, following the New York Yankees' Alex Rodriguez last February. Big Mac and A-Rod, coincidentally, are currently tied on the home-run list.
San Francisco Giants manager Bruce Bochy expects more players to admit what they did.
"The ones who have come forward and been straight have been forgiven, and they've moved on," he said. "The fans and baseball have dealt with them in a positive way."
Besides Bonds, others facing questions include Roger Clemens, Manny Ramirez and David Ortiz. Like Bonds, they have denied knowingly using illegal or banned substances. Clemens is under investigation by a federal grand jury trying to determine whether he lied to a congressional committee.
McGwire said he hoped to come forward at the congressional hearing, when he sat alongside Sosa and Rafael Palmeiro, who denied using steroids but tested positive for one later that year.
"I wanted to get this off my chest, I wanted to move on, but unfortunately immunity was not granted," he said.
McGwire's lawyers, Mark Bierbower and Marty Steinberg, told him that if he made any admission, he could be charged with a crime and that he, his family and friends could be forced to testify before a grand jury.
"That was the worst 48 hours of my life, going through that, but I had to listen to the advice of my attorneys," he said.
He knew that Don Hooton, whose son's suicide was linked to steroid use, was in the audience.
"Every time I'd say, 'I'm not going to talk about the past,' I'd hear moanings back there. It was absolutely ripping my heart out," McGwire said, his voice cracking. "All I was worried about was protecting my family and myself. And I was willing to take the hit."
Bierbower told the AP in a telephone interview that he had instructed McGwire not to make any admissions before Congress.
"He also had a situation where his brother had been giving him steroids and he didn't want to create a risk for his brother, either," Bierbower said.