The cardiovascular response to coitus and the risk of an acute cardiac event related to sexual activity is of clinical importance, especially now that effective pharmacologic treatment of male erectile dysfunction permits older men to resume active sex lives. Early studies by Masters and Johnson of young subjects engaging in coitus in laboratory settings reported that heart rates and systolic blood pressures were at near maximum exercise levels. Subsequent data from studies by Hellerstein and Friedman and by Stein in men with coronary artery disease, using ambulatory electrocardiographic recordings during coitus at home, demonstrated significantly lower heart rate and blood pressure responses to coitus. The associated myocardial oxygen demand of coitus in these men was found to in the range of moderate activities, often achieved or exceeded during their workday. The cardiovascular risk of coitus was addressed in the recent ONSET study in which myocardial infarction (MI) patients were interviewed shortly after their MI about potential triggering activities or events. Coitus was noted to represent a very low absolute risk of being a trigger for MI, but had an increased relative risk of 2.5 for the subjects in their study. Sexual intercourse will, in most men, represent only a moderate "stress" on the heart in terms of the responses that impact on myocardial oxygen requirement (heart rates, and systolic blood pressure). In patients with coronary artery atherosclerosis, coitus, compared with vigorous physical activity and intense emotional responses, represents a small risk of triggering an acute MI.