Objective To determine what the tobacco industry knew about menthol's relation to smoking cessation behaviour.

Methods A snowball sampling design was used to systematically search the Legacy Tobacco Documents Library (LTDL) (http://legacy.library.ucsf.edu) between 15 May to 1 August 2010. Of the approximately 11 million documents available in the LTDL, the iterative searches returned tens of thousands of results. A final collection of 509 documents relevant to 1 or more of the research questions were qualitatively analysed, as follows: (1) perceived sensory and taste rewards of menthol and potential relation to quitting; and (2) motivation to quit among menthol users.

Results Menthol's cooling and anaesthetic effects mask the short-term negative physiological effects of smoking such as throat pain, burning and cough. This provides superficial physical relief as well as psychological assurance against concerns about the health dangers of smoking that would otherwise motivate smokers to quit. Menthol smokers, particularly women, perceive the minty aroma of menthol cigarettes to be more socially acceptable than non-menthol cigarettes.

Discussion Consumers believe menthol's sensory effects equate to health protections and that menthol cigarettes are more socially acceptable than non-menthol cigarettes. Menthol in cigarettes may encourage experimenters who find non-mentholated cigarettes too harsh, including young or inexperienced users, to progress to regular smoking rather than quitting, and may lessen the motivation to quit among established menthol smokers. The perception of menthol cigarettes as more socially acceptable lessens the impact of smoking denormalisation on quitting motivation. Menthol makes cigarettes easier and more palatable to smoke and less desirable to quit among established smokers. Fewer smokers quitting contributes to the incidence of tobacco-related diseases.