Still Secret After 30 Years? As the misguided war in Iraq made clear, intelligence analysis is an uncertain game, all too vulnerable to error and politically motivated distortion. That experience has done little to change the intelligence community's passion for secrets, whether or not they need to be kept. Three decades later, we still do not know for certain - but have good reason to believe - that flawed or distorted intelligence led the Reagan administration to accuse the Soviet Union and Vietnam of using chemical weapons, known as yellow rain. A classified critique of the intelligence behind those charges, written several years ago for the Central Intelligence Agency, could shed light on what happened. Last year, Matthew Meselson, a Harvard expert on chemical and biological weapons, filed a Freedom of Information Act request to get the report released. He was turned down. The report should be made public both for its historical value and its possible lessons on how to handle the challenge of divining an enemy's capabilities and intentions. In 1981 and 1982, the Reagan administration charged that the Soviet Union had supplied toxins made from a poisonous fungus to its Vietnamese and Laotian allies to use as a weapon against Hmong villagers who had sided with the United States during the Vietnam War and against anti-Vietnamese forces in Cambodia. The charge was based on circumstantial evidence, including reports from Hmong refugees who claimed to have been sickened by the attacks, and by laboratory tests that purported to find traces of toxins in yellow spots scraped from foliage and in the blood or urine of supposed victims. Over the years, skeptics - led by Dr. Meselson - have persuasively disputed most of the claims but left some loose ends. They argued that the yellowish drops found on foliage were most likely produced by honeybees, which often leave their nests en masse and produce showers of pollen-laced feces that can cover an acre or more with hundreds of thousands of yellow spots. They suspect but cannot prove that the traces of poison found in some samples were false positives caused by laboratory contamination. Defense laboratories in the United States, Britain, France and Sweden analyzed scores of samples and never found a trace of poison. Meanwhile, the testimony by Hmong refugees usually fell apart in follow-up interviews. Their illnesses were repeatedly shown to be due to natural causes. No chemical munitions have ever been found, and none of the hundreds of Vietnamese soldiers who were debriefed provided a shred of information that suggested the use of a weapon remotely resembling yellow rain. The internal report that Dr. Meselson is seeking was done by a former covert operative and contract historian, and examined how the intelligence community came up with its finding that "yellow rain" was a chemical weapon. The C.I.A. is claiming that releasing the report would reveal sensitive information about intelligence sources and methods, as well as the organization and function of the C.I.A. Thirty years later, that is preposterous. A better guess is that the agency is worried about being embarrassed by what the report says about how the intelligence community did its work.