In a population-based study of 590 Rancho Bernardo, California men aged 30-79 years without a history of cardiovascular disease, and who were first surveyed in 1972-1974, current cigarette smokers had significantly higher mean endogenous androstenedione, estrone, and estradiol levels compared to nonsmokers. In the cigarette smokers, a dose-response relationship was apparent for these hormones with mean levels increasing with increasing reported cigarette consumption. These differences persisted after adjusting for age and body mass index, and were not accounted for by either caffeine or alcohol intake, or exercise habit. In a further 89 men with a history of cardiovascular disease, hormone levels were not significantly related to smoking habit. The higher endogenous estrogen levels in cigarette smokers may confound the interpretation of studies reporting higher estrogen levels in male myocardial infarction survivors compared to controls.