McGwire said he also used human growth hormone, and he didn't know if his use of performance-enhancing drugs contributed to some of the injuries that led to his retirement, at age 38, in 2001.

"That's a good question," he said.

He repeatedly expressed regret for his decision to use steroids, which he said was "foolish" and caused by his desire to overcome injuries, get back on the field and prove he was worth his multimillion-dollar salary.

"You don't know that you'll ever have to talk about the skeleton in your closet on a national level," he said. "I did this for health purposes. There's no way I did this for any type of strength use."

McGwire hit a then-record 70 homers in 1998 during a compelling race with Sammy Sosa, who finished with 66.

On Monday, McGwire called Pat Maris, the widow of Roger Maris, who had held the home run record with 61 in 1961, and admitted taking steroids.

"I felt that I needed to do that," McGwire told Costas. "They've been great supporters of mine. She was disappointed and she has every right to be."

Told by Costas that certain Maris family members have said that they now consider Roger Maris' 61 the authentic home run record, McGwire responded: "They have every right to."

Maris' son Rich told the San Francisco Chronicle that McGwire was "pretty choked up" when he called Pat Maris.

"My mom was very touched by his call. She felt sorry for Mark -- that he's going through this. She conveyed that we all make mistakes and move on from there," Rich Maris told the newspaper.

"[McGwire's steroid use] is something we thought all along. It wasn't so much a surprise, but I feel bad for Mark. He's a very genuine guy and we're close to him -- we love him like a brother. I'm glad he got it out," Maris told the newspaper.

But McGwire consistently asserted that he would have hit home runs without PEDs.

"There's not a pill or an injection that's going to give me, going to give any player the hand-eye coordination to hit a baseball," McGwire told Costas.

More than anything else, the home run spree revitalized baseball following the crippling strike that wiped out the 1994 World Series. Now that McGwire has come clean, increased glare might fall on Sosa, who has denied using performing-enhancing drugs.

McGwire did not name specific drugs that he took.

"The names I don't remember, but I did injectables," McGwire told Costas. "I preferred the orals. The steroids I took were on a very low dosage."

McGwire said that he didn't want to bulk up.

"I took very low dosages because I wanted my body to feel normal," he said.

McGwire admitted that a shadow hangs over his time in baseball, however.

"I wish I had never played during the steroid era," he said to the AP.

McGwire's decision to admit using steroids was prompted by his decision to become hitting coach of the St. Louis Cardinals, his final big league team. La Russa, McGwire's manager in Oakland and St. Louis, has been among McGwire's biggest supporters and believes returning to the field can restore the former slugger's reputation.

"He found out this morning," McGwire told Costas of La Russa. "He's like talking to my dad. I've let a lot of people down."

La Russa told ESPN that his feelings haven't changed about McGwire's joining the team as hitting coach.

"I never knew when, but I always knew this day would come," McGwire said. "It's time for me to talk about the past and to confirm what people have suspected."

McGwire knew that his hiring would create a firestorm.

"I was the one who went to the Cardinals and said, 'We have to do something about this. I have to come clean,'" he told Costas.

McGwire, who is eighth on the all-time home run list with 583 homers, was not elected into the Hall of Fame in his fourth year of eligibility. In voting that was announced on Jan. 6, he received 128 votes (23.7 percent) in the balloting, 10 more than last year and matching the total from his first two times on the ballot.

Asked by Costas if he would vote for himself, McGwire said: "If I had a Hall of Fame vote? I'd leave it up to you guys. I'll leave it up to the writers."

Indians Hall of Famer pitcher Bob Feller, 91, doesn't believe McGwire's admission will help him much with voters.

"It'll help him some, but not very much," Feller told Willie Weinbaum of the ESPN Enterprise Unit. "I wouldn't vote for him and I don't think he'll get into the Hall of Fame in my lifetime."

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.

Others have been tainted but have denied knowingly using illegal substances, including Barry Bonds, Roger Clemens and David Ortiz.

"I don't think any of the steroid boys will be in the Hall of Fame for 25, 30 years," Feller said. "I think Clemens has been lying through his teeth. In my opinion, Bonds did take steroids."

Bonds has been indicted on charges he made false statements to a federal grand jury and obstructed justice. Clemens is under investigation by a federal grand jury trying to determine whether he lied to a congressional committee.

"I'm sure people will wonder if I could have hit all those home runs had I never taken steroids," McGwire said. "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."

Big Mac's reputation has been in tatters since March 17, 2005, when he refused to answer questions at a congressional hearing. Instead, he repeatedly said, "I'm not here to talk about the past," when asked whether he took illegal steroids when he hit a then-record 70 home runs in 1998, or at any other time.

"After all this time, I want to come clean," he said. "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."

McGwire said he wanted to tell the truth then but evaded questions at that hearing on the advice of his lawyers.

"I wanted to talk about this," McGwire said to Costas. "I wanted to get this off my chest. We didn't get immunity. So here I am in this situation with two scenarios: possible prosecution or possible grand jury testimony."

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. He decided not to talk about the past.

"That was the worst 48 hours of my life, going through that, but I had to listen to the advice of my attorneys," McGwire said.

He knew that Don Hooton, whose son had died from steroids 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.

In the interview with ESPN, La Russa said of McGwire's testimony: "The one thing he did not do is lie. And I don't think he ever would."

Tom Davis was the chairman of the Committee on Oversight and Government Reform on March 17, 2005, when McGwire repeatedly testified that he would not "talk about the past."

Davis told the AP on Monday that McGwire made clear the day before that hearing he had used steroids and wanted to say so but was worried he would face legal trouble by admitting it then. Davis says he was turned down when he asked then-Attorney General Alberto Gonzalez to grant McGwire immunity.

Says Davis: "He was candid and honest in our interrogation of him. He said: 'Some day, I'll tell the story.'"

La Russa immediately praised McGwire's decision to go public.

"His willingness to admit mistakes, express his regret, and explain the circumstances that led him to use steroids add to my respect for him," the manager said.

McGwire disappeared from the public eye following his retirement as a player following the 2001 season. When the Cardinals hired the 47-year-old as coach on Oct. 26, they said he would address questions before spring training, and Monday's statement broke his silence.

"I remember trying steroids very briefly in the 1989-1990 offseason and then after I was injured in 1993, I used steroids again," McGwire said in his statement. "I used them on occasion throughout the '90s, including during the 1998 season."

McGwire said he took steroids to get back on the field, sounding much like the Yankees' Andy Pettitte did two years ago, when he admitted using HGH.

"During the mid-'90s, I went on the DL seven times and missed 228 games over five years," McGwire said. "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."

He said he first used steroids between the 1989 and 1990 seasons, after helping the Athletics to a World Series sweep when he and Jose Canseco formed the Bash Brothers.

"When you work out at gyms, people talk about things like that. It was readily available," he said. "I tried it for a couple of weeks. I really didn't think much of it."

Canseco has written in his book that he injected steroids in the A's clubhouse with McGwire.

"There's absolutely no truth to that whatsoever," McGwire told Costas.

He said 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 truly believe I was given the gifts from the Man Upstairs of being a home run hitter, ever since ... birth," McGwire said. "My first hit as a Little Leaguer was a home run. I mean, they still talk about the home runs I hit in high school, in Legion ball. I led the nation in home runs in college, and then all the way up to my rookie year, 49 home runs.

"But, starting '93 to '94, I thought it might help me, you know, where I'd get my body feeling normal, where I wasn't a walking MASH unit," he said.

And there was the pressure of living up to his previous performance and his multimillion-dollar salary, McGwire said, adding that he was "getting paid a lot of money to try to stay up to that level."

Feller isn't buying that McGwire's performance wasn't helped by steroids.

"I think that's a lot of horse muffins," he said. "If it didn't help him any, what the hell was he taking them for? Of course it helped him."

Ralph Houk, Maris' manager with the Yankees in 1961, told ESPN that he does not think the legitimacy of McGwire's home run totals is changed by his admission of using performance-enhancing drugs and that the effects of such drugs -- whether pills (amphetamines) taken in the 1960s or steroids in later years -- are questionable.

"I think [McGwire] broke [Maris'] record fairly," Houk told ESPN.

"I wouldn't be concerned about it. [McGwire] was a good hitter that deserves everything he's got," Houk said.

Since the congressional hearing, baseball owners and players toughened their drug program twice, increasing the penalty for a first steroids offense from 10 days to 50 games in November 2005 and strengthening the power of the independent administrator in April 2008, following the publication of the Mitchell report.

"Baseball is really different now -- it's been cleaned up," McGwire said. "The commissioner and the players' association implemented testing and they cracked down, and I'm glad they did."

Victor Conte, who has been at the center of the steroid scandal as founder and president of the Bay Area Laboratory Co-operative (BALCO), praised McGwire.

"I respect Mark McGwire for finally coming forward and telling the truth regarding his use of PEDs," Conte said in an e-mail to ESPN.com. "I believe he received bad advice when he refused to admit his drug use five years ago before Congress. We live in a society that will forgive us for our mistakes, if we are honest and accept responsibility.

"The athletes that have admitted to their use of PEDs have been able to move on with their careers and lives. Those who continue to lie about their drug use will remain under dark cloud. I urge the athletes that have used drugs in the past to come clean, so that we can move on."

Information from The Associated Press and ESPN's Willie Weinbaum was used in this report.