The three Canadian researchers published copies of 60 internal documents, shredded by Imperial Tobacco Canada in 1992 to avoid embarrassment or liability, in the Canadian Medical Association Journal.
The copies were uncovered in the files of parent firm British American Tobacco subsidiary.
The documents detail evidence from scientific reviews prepared by British American Tobacco's researchers, as well as dozens of original research studies between 1967 and 1984, such as the examination of the biological activity and carcinogenicity of tobacco smoke.
They describe research on cigarette modifications and toxic emissions, including how consumers adapted their smoking behavior to these modifications, and depict a comprehensive research program on the pharmacology of nicotine and its central role in smoking behavior.
Some studies found second-hand smoke on rats was dangerous. Other research cast doubt on the comparative benefits of low-tar cigarettes, as smokers simply compensated by inhaling more intensely.
All the while, Imperial Tobacco Canada executives had denied that smoking was addictive or a health hazard, even testifying such at a parliamentary committee hearing in 1987.
The records are now likely to be used in lawsuits by three Canadian provinces seeking billions of dollars from tobacco firms for smoking-related health care costs.