In 15 years of previously undisclosed research, the world's largest tobacco company studied nicotine and found that it affected the body, brain and behavior of smokers.
That work is at odds with arguments by the company, Philip Morris, that nicotine should not be regulated under laws applying to drugs that affect the body.
About 2,000 pages of documents obtained by the New York Times show that the company's researchers used laboratory methods that are customarily employed in assessing drugs to study the effects of nicotine on smokers, and wrote about what they described as the "pharmacologic" effects of nicotine.
Although the company has asserted that it does not manipulate the levels of nicotine in its products, the documents also show that Philip Morris studied different levels of nicotine in cigarettes to find what was pleasing to smokers.
Charles R. Wall, a Philip Morris lawyer, said yesterday that he was familiar with the documents, acknowledging they showed that the company carried out extensive research on nicotine over many years and manipulated nicotine levels in test cigarettes. But he said the research was never used in creating products for the market.
But critics of tobacco companies say the studies described in the documents show that Philip Morris understood more completely than it has publicly acknowledged the effects of its products on smokers and failed to disclose what it knew to customers or regulators.
The documents are coming to light as the Food and Drug Administration investigates whether nicotine should be regulated as a drug under the law. That would allow the government to restrict the way cigarettes are made and sold. Federal law states that a substance must be regulated as a drug if the manufacturer intentionally uses it to "affect the structure or function of the body" of consumers.
The Philip Morris research on nicotine comes mostly from the company's research center in Richmond, Va., and is dated from 1966 to 1981. The documents were made available on the condition that the source not be identified other than as a person involved in "anti-smoking work."
That person said the documents, which were part of a lawsuit but had not been made public, came from a confidential source.
Among other things, the documents show the following:
* College students were the subjects for much of Philip Morris' research for more than 15 years, and one study, based on a questionnaire about smoking habits in an Iowa town, included teen-agers as young as 14.
* The Philip Morris files contained information on the federal government, anti-tobacco groups and tobacco researchers, even some whose work the tobacco companies had paid for. Among that information were internal documents from the Department of Health, Education and Welfare as well as from the American Cancer Society and the National Association of Broadcasters, which was at the time opposing the HEW secretary's proposal that broadcasters be required to run anti-smoking messages.
Dr. Victor DeNoble, who was a research scientist in Philip Morris' Richmond, Va., laboratories from 1980 to 1984 and is familiar with the documents, said the most crucial finding in the research was this:
"The company began to realize that they could reduce the tar, but increase the nicotine, and still have the cigarette be acceptable to the smoker. After all their work, they realized that nicotine was not just calming or stimulating, but it was having its effect centrally, in the brain, and that people were smoking for brain effects" -- a mild high that induces craving.
Aside from possibly affecting future regulatory action, the documents could become legal evidence. A consortium of nearly 60 law firms has mounted the largest class action in history, charging that the seven major tobacco manufacturers, including Philip Morris, and the Tobacco Institute, an industry group, concealed knowledge that nicotine was addictive and manipulated nicotine levels to keep smokers addicted.