"I injected him probably twice," adds Canseco. "But it wasn't like, I mean, we would just walk in and a lot of times they were pill form. A lot of times, you would just, a quick injection of whatever and that's it."

"I'm just repeating what you say in the book," says Wallace. "And if we're to believe what you say in the book, 'I would often,' not twice, 'inject Mark.'"

"Well, I think it was more inject ourselves. I think I injected him. I mean, this is a long time ago. Once or twice for sure," says Canseco. "I didn't keep track, but an athlete may prepare his needle and may ask another athlete to inject him quickly. And that's the way it works."

"And these were not allowed at that time in the league," asks Wallace.

"Absolutely no," says Canseco.

In a statement to 60 Minutes, McGwire said: "Once and for all, I did not use steroids nor any illegal substance. I feel sorry to see someone turn to such drastic measures to accomplish a personal agenda at the expense of so many. The relationship that these allegations portray couldn't be further from the truth. Most concerning to me is the negative effect that sensationalizing steroids will have on impressionable youngsters who dream of one day becoming professional athletes."
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Both McGwire and Canseco played under manager Tony La Russa in Oakland.

"Jose Canseco says that he and Mark McGwire used anabolic steroids a lot when you were managing them back at the Oakland A's. True," Wallace asks La Russa.

"I don't think there's any doubt that it's a fabrication," says La Russa. "The product of our good play and the size and strength of our players -- Mark was a great example. What we saw was a lot of hard work. And hard work will produce strength gains and size gains."

"Why do you think that Canseco says that McGwire was using. Honest," asks Wallace.

"First of all, I think he's in dire straits and needs money," says La Russa. "I think secondly, I think there's a healthy case of envy and jealousy."

Sports writer Howard Bryant covered baseball as a beat writer for six seasons. He's currently writing a book about the past 10 years of baseball, a time some call "The Steroid Era."

"Here's what Tony La Russa says about Mark McGuire. 'I am absolutely certain Mark has earned his size and strength from hard work and a disciplined lifestyle.' Reaction," Wallace asks Bryant.

"I think that if there's anything that we're being taught about this story, it's that Mark McGwire has a lot more friends than Jose Canseco," says Bryant.

And for good reason, says Bryant. Canseco's alleged character flaws are many - including greed, which is evidenced by the fact that he charged his fans $2,500 a day to spend time with him at his home when he was under house arrest for parole violation.

Still, Bryant says Canseco's accusations on the subject of steroids should not be taken lightly.

"I think the reason why Jose Canseco is going to catch a lot of hell for his book is because people believe he's full of it. He hasn't been credible. He hasn't been a credible player. He is a snitch, which is the worst thing you can possibly be in the ironclad baseball fraternity," says Bryant.

"He's done a lot of things to offend a lot of people. On this subject, however, I believe he does have some credibility."
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Canseco's first stint in Oakland ended in 1992, when he was traded to the Texas Rangers. Among his new teammates were future American League MVPs Juan Gonzalez and Ivan Rodriguez, as well as Rafael Palmeiro, who played against Canseco when the two of them were youngsters growing up in Miami.

In his book, Canseco writes that he used anabolic steroids with all three players.

"In '92, you were traded to the Texas Rangers," says Wallace. "Did you teach your new teammates how to use steroids?"

"Yes. We spoke and educated three or four players there. ... Rafael Palmeiro, Juan Gonzalez, Ivan Rodriguez," says Canseco. "I injected them. Absolutely."

All three players have vehemently denied the allegations. Palmeiro's lawyer sent 60 Minutes a letter stating that: "Mr. Palmeiro categorically denies that he has ever engaged in illicit use of steroids or any substance banned by Major League Baseball."

Canseco spent three seasons in Texas, and then two in Boston, before rejoining McGwire at the Oakland A's in 1997. Another young player there at the time was Jason Giambi, who won the MVP award in 2000 and later went to the New York Yankees for a blockbuster $120 million, seven-year contract.

Canseco writes that Giambi was the most obvious steroid user in baseball. "We spoke about it quite in depth," says Canseco. "And you know, when I rejoined the team back in '97, we'd be working out, talking about it. You know, we'd go into clubhouses and do steroids. Bottom line."

He writes that "Giambi, McGwire, and I talked about steroids all the time."

"Especially in '97, yes. Especially when we were working out," says Canseco. "We talked about what each does."

"So you'd shoot up steroids and growth hormones with Jason Giambi as well," asks Wallace.

"Yes, Oh yeah," says Canseco. "I mean, it wasn't a big deal. It was common ground."

According to the San Francisco Chronicle, Giambi did admit to a federal grand jury that he had been using steroids at least since 2001. He told reporters last Thursday, about what Canseco said, "I think it's sad. I think it's delusional."
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In his book, Canseco contends that Major League Baseball's establishment had to know of the growing use of illegal steroids. He alleges that the owners; Donald Fehr, the head of the players union; and Bud Selig, the game's commissioner were all turning a blind eye.

"To me, Bud Selig, he'll be defined by how this era is viewed in history. I mean, you are looking at a baseball establishment that has said that it wanted to get rid of steroids for 10 years, yet I don't recall baseball ever doing a public service announcement saying to kids, 'Hey kids, don't do this. This is bad for you,'" says Bryant.

"I don't recall baseball ever doing an independent investigation. They haven't spent a penny, at least to my knowledge, to go out and investigate, and find out what's going on with this steroid business."

Selig declined to talk to 60 Minutes. As for Canseco, he is unrepentant. And perhaps the most astonishing thing about his book, in the face of widespread medical evidence that the abuse of anabolic steroids causes serious health problems, is that he still endorses the use of steroids.

"I don't recommend steroids for everyone, and I don't recommend growth hormones for everyone," says Canseco. "But for certain individuals, I truly believe, because I've experimented with it for so many years, that it can make an average athlete a super athlete. It can make a super athlete --incredible. Just legendary."

Major League Baseball now has a new policy on players' use of anabolic steroids. First offense is a 10-day suspension; by the fourth offense, it's a one-year suspension. And U.S. Olympic policy on steroids puts a two-year ban from all international competition for first offenders.