But challenges are expected from players cited in the report, which is based largely on testimony from former New York Mets clubhouse attendant Kirk Radomski, who cooperated as part of a plea deal with federal authorities after his arrest for distribution of illegal substances.

The 311-page Mitchell Report, for instance, made its biggest splash by naming pitching great Roger Clemens among more than 50 players not previously linked to doping.

Clemens, a seven-time winner of the Cy Young award as his league's best pitcher, issued an angry denial to allegations that filled nine pages of the report.

"Roger has been repeatedly tested for these substances and he has never tested positive," his attorney Rusty Hardin said.

"Roger Clemens adamantly, vehemently or whatever adjective can be used, denies he has ever used steroids or whatever the word is for improper substance."

Clemens joined home-run king Barry Bonds as the two most celebrated players to have allegedly used drugs to gain a competitive advantage.

Bonds is to stand trial on charges of lying to a grand jury when he denied using steroids.

CONDUCT "SO SERIOUS"

The Mitchell report advised against disciplining players for past use unless Major League Baseball's commissioner believes "the conduct is so serious that discipline is necessary to maintain the integrity of the game."

"His report is a call to action, and I will act," Selig vowed. "I'm going to review his findings and the factual support. Punishments will be taken on a case-by-case basis."

Mitchell failed to receive cooperation from players and interviewed only two current major leaguers during his probe.

The head of the World Anti-Doping Agency, Dick Pound, called the behavior of the players' association, which gave limited assistance to Mitchell, mostly "a disgrace and an outrage."

Major League Baseball Players Association chief Donald Fehr was foremost among those who said players may have been treated unfairly.

"Many players were named. Their reputations have been adversely affected, probably forever, even if it turns out down the road that they should not have been named," he told a news conference.

"Anyone interested in fairly assessing allegations against the players should consider the nature of the evidence presented, the reliability of the source."

Selig set a precedent last week in handing down 15-game suspensions to Jose Guillen and Jay Gibbons for procuring performance-enhancing drugs in 2004.

Those penalties were based on a more lenient punishment scale used at that time. Under today's more punishing policy, a first offense brings a 50-game suspension.

There are millions to be made if a player can perform at the big league level. Guillen, for instance, was signed to a three-year, $36 million contract by the Kansas City Royals one month after he became formally linked to drug use.

Some old-time players feel differently about players suspected of cheating.

Hall of Fame pitcher Bob Feller, 89, said he would not welcome such players into baseball's most hallowed club.

"Baseball is a game of rules and when you break the rules I don't think you should be part of the Hall of Fame," Feller told Reuters.

Copyright © 2007 Reuters Limited. All rights reserved. Republication or redistribution of Reuters content, including by framing or similar means, is expressly prohibited without the prior written consent of Reuters. Reuters shall not be liable for any errors or delays in the content, or for any actions taken in reliance thereon. Reuters and the Reuters sphere logo are registered trademarks and trademarks of the Reuters group of companies around the world.