The Bush administration is taking wide measures to tighten scientific secrecy in the hope of keeping weapons of mass destruction out of unfriendly hands.
Last month, it began quietly withdrawing from public release more than 6,600 technical documents that deal mainly with the production of germ and chemical weapons. It is also drafting a new information security policy, to be released in the next few weeks, that officials say will result in more documents' being withdrawn. It is asking scientific societies to limit what they publish in research reports.
''We're working hard for a set of guidelines so terrorists can't use information that this country produces against us,'' Tom Ridge, the director of homeland security, said in an interview. ''This will have to be a dynamic process.'' He added that scientists were being closely consulted on any new guidelines.
But critics say the most extreme steps proposed could make it impossible for scientists to assess and replicate the work of their colleagues, eroding the foundations of American science. They fear that government officials eager for the protections of secrecy will overlook how open research on dangerous substances can produce a wealth of cures, disease antidotes and surprise discoveries.
''It comes down to a risk-benefit ratio,'' said Robert R. Rich, president of the Federation of American Societies for Experimental Biology. ''I think the risk of forgone advances is much greater than the information getting into the wrong hands.''
The federal reports already withdrawn, once sold freely to the public, include not only declassified ones from the 1940's, 50's and 60's but also modern ones that were previously judged to contain nothing that had to be kept secret. Experts say the sweeping withdrawal has few if any precedents.
R. Paul Ryan, deputy administrator of the federal Defense Technical Information Center, the Pentagon agency that has custody of the reports, said panels of scientific experts would be assembled to see whether the documents should once again be made available to the public or perhaps reclassified as state secrets.
The expert panels, he said, will determine ''if we need major, minor or no revisions'' to security guidelines.
Mr. Ryan added that he did not know when such deliberations might be completed or decisions made over the fate of the 6,600 withdrawn documents.
Since Sept. 11, the administration has sought to clamp down on the flow of information on several fronts. In October, for example, Attorney General John Ashcroft told federal officials that the Justice Department would support them if they resisted freedom-of-information requests. But science has now become the leading edge of the crackdown.
For instance, the White House has asked the American Society of Microbiology, the world's largest group of germ professionals, based in Washington, to limit potentially dangerous information in the 11 journals it publishes, including Infection and Immunity, The Journal of Bacteriology and The Journal of Virology.
One White House proposal is to eliminate the sections of articles that give experimental details researchers from other laboratories would need to replicate the claimed results, helping to prove their validity.
''That takes apart the whole foundation of science,'' Ronald M. Atlas, president-elect of the society, said of omitting methods. ''I've made it reasonably clear that we would object to anything that smacked of censorship. They're discussing it, and I wouldn't rule out them doing something.''
He added that he was surprised by the number of his colleagues in academia who seemed willing to discuss publishing limits. ''I think it undermines science,'' he said.
Abigail Salyers, the society's president, offered a more pointed rebuff. ''Terrorism feeds on fear, and fear feeds on ignorance,'' she said in a statement to appear in the March issue of the group's magazine. The best defense against anthrax or any infectious disease, Dr. Salyers added, is information that can bolster public safety.