"We made every effort to establish the truthfulness of the information that we received," baseball's steroids investigator said Friday during a half-hour interview at his law office. "Several of the witnesses were interviewed in the presence of federal law enforcement agents who informed the witnesses that if they made false statements they would subject themselves to possible criminal jeopardy. So there was very strong incentives to tell the truth."

A day after Mitchell issued a searing report that implicated Clemens, seven former MVPs and more than 80 players in all, President Bush said he's been "troubled by the steroid allegations."

Mitchell said he included in his report nearly all those who were implicated in his investigation. Players largely declined to interview with Mitchell.

"There were two players whose names I did not publish because the allegations occurred after the time that they had left baseball," he said.

The 74-year-old former Senate majority leader, hired by baseball commissioner Bud Selig in March 2006, wouldn't put a precise figure on how many major leaguers used performance-enhancing drugs.

"It is my judgment that the 5-7 percent that tested positive in the 2003 anonymous survey testing understated the amount of use, but I don't think it reaches a majority. I think it is a minority, albeit a significant minority," he said. "That's why I think that the majority of players who don't use such substances are principal victims of what has occurred. They follow the rules. They obey the law and they are placed in a position where they have to make the awful choice between either becoming illegal users themselves or being put at a competitive disadvantage."

Although he received cooperation from the Justice Department, Mitchell said he did not obtain evidence from the Albany, N.Y., district attorney, who has been investigating a drug ring that sold to players. He also said he never got complete copies of sworn statements by IRS special agent Jeff Novitzky that implicated players but were released publicly with the names blacked out.

Because it was a private inquiry, Mitchell said he did not think a standard of evidence was necessary.

"It is not a judicial proceeding. It is not a trial," he said. "But it doesn't make any difference what standard or what court you're in: direct, personal, eyewitness testimony, it is the principal form of evidence in most proceedings."

Much of his evidence came from former Mets clubhouse attendant Kirk Radomski and former Yankees strength coach Brian McNamee, who said he personally saw use by Clemens and Andy Pettitte.

Clemens' lawyer vehemently denied the accusations against the seven-time Cy Young Award winner, whose Hall of Fame chances might have been damaged by Mitchell's report. Pettitte's agent, Randy Hendricks, has advised his client not to comment because he is an active player.

Although Radomski didn't see players inject drugs, his records and story were compelling to Mitchell.

"If someone makes one purchase and says he didn't use it, that's one thing," Mitchell said. "If someone makes three, four, five, six, seven purchases over a period of several months or years, it obviously raises the question: If you weren't using it, why were you continuing to buy it?"

Sitting in a conference room, a plant behind his chair to add a scenic background, Mitchell said his next big task would be to start treatment for prostate cancer, an illness he made public in August. He said he was told his prognosis is good.

Although he thinks drug testing is essential in baseball, he didn't agree that congressional representatives, judges and the president and vice president should set an example by also submitting to tests.

"I don't think one can make a blanket statement that all people should be tested," he said. "It obviously requires a case-by-case analysis."