This article addresses the controversial issue of whether non-smokers' exposure to environmental tobacco smoke (ETS) increases their risk of developing coronary heart disease (CHD). Glantz and Parmley purport to provide toxicological and epidemiologic evidence in support of their contention that non-smokers who are exposed to ETS are more likely to develop CHD than non-smokers who are not so exposed. The toxicological evidence provided by Glantz and Parmley has been challenged by Wu and by Gori, among others. Moreover, the epidemiologic data considered by Glantz and Parmley are equivocal at best and do not include data from the American Cancer Society's Cancer Prevention Studies (CPS-I) and (CPS-II and the National Mortality Followback Survey which, when added to the original epidemiologic database considered by Glantz and Parmley, indicate no statistically significant association. Furthermore, most of the epidemiologic studies indicate a myriad of biases and confounders that have not been adequately adjusted. Many primary risk factors that were identified in the premier heart disease study, the Framingham Study (Kannel et al.), including but not limited to ethnicity, family history, dietary habits, age, serum cholesterol, exercise and alcohol use, were either totally ignored or not adequately considered in the epidemiologic studies. It seems foolhardy, then, to claim an association as do Glantz and Parmley. But perhaps a more egregious breach of science is to predict a number of CHD deaths in non-smokers caused by ETS. Unfortunately, that is what Wells purports to do. When one considers all the available evidence, the only reasonable conclusion that can be reached is that no association has been established between ETS exposure in non-smokers and an increased risk of CHD. © 1998 John Wiley & Sons, Ltd.