The role of pulmonary function as an independent predictor of coronary heart disease was examined in 1965-1983 in a cohort of Japanese-American men. As part of the Honolulu Heart Program, the authors measured pulmonary function in 5,924 men aged 45-68 years who were free of coronary heart disease at baseline examination and followed them for 15-18 years for the development of nonfatal myocardial infarction and fatal coronary heart disease. Per cent predicted forced expiratory volume in one second (%PFEV1) was significantly inversely related to coronary heart disease incidence in the total cohort after adjusting for age (p less than 0.0001) and then for all known coronary heart disease risk factors (p = 0.0004). However, when examined by smoking status, %PFEV1 was a predictor of coronary heart disease only among past and current smokers, and not for men who had never smoked cigarettes (p = 0.36). The association between pulmonary function and coronary heart disease can be explained by cigarette smoking, which leads to both lung impairment and coronary heart disease incidence.