Recent studies have reported higher plasma estradiol levels in male survivors of acute myocardial infarction. This finding has raised the possibility that hyperestrogenemia may consitiute a separate coronary risk factor. In 443 men, aged 30, 40, 50, and 60, we assessed the relationship between plasma levels of estradiol, testosterone, and testosterone-binding globulin and coronary risk factors: fasting plasma concentrations of triglyceride, cholesterol, and high-density lipoprotein, blood pressure, and smoking and leisure-time physical activity patterns. Plasma estradiol concentrations were found to correlate significantly with body weight. After adjustment for this association, we found that the mean plasma estradiol concentration still was significantly higher in smokers than in nonsmokers. No other correlation could be estabilished between plasma hormone levels and coronary risk factors. The relative hyperestrogenemia reported in men with previous myocardial infarction may be due to an effect of smoking but may also reflect the relationship between body weight and plasma estradiol levels. Future studies should consider the demonstrated association between plasma estrogen levels and smoking.