Sildenafil citrate is the first oral agent approved for the treatment of erectile dysfunction (ED); other oral agents are in the process of development. Because the mechanism of action of many of these agents involves vasodilation, there is a potential for interaction with the cardiovascular system. Sildenafil inhibits phosphodiesterase-5 (PDE-5) which is found in the corpus cavernosum and in the systemic vasculature. Sildenafil causes a mild decrease in systemic arterial pressure ( approximately -8/-5.5 mm Hg); it causes a synergistic and often major decrease in systemic arterial pressure in the presence of organic nitrates (nitric oxide donors). Sildenafil is therefore contraindicated in patients taking organic nitrates. A review was made of clinical trials in populations of men with (1) erectile dysfunction; (2) chronic stable ischemic heart disease and erectile dysfunction; and (3) hypertension and erectile dysfunction. This review showed that sildenafil was effective and not associated with an increase in serious cardiovascular adverse events, myocardial infarction (MI), or death compared with placebo. Although there have been spontaneous reports of death among men using sildenafil, there are limitations to spontaneous-event reporting. In addition. the numbers of such reports are well below the expected numbers of deaths when considering the number of men who have received prescriptions for sildenafil and their age and cardiovascular risk factor profile. Because there is a small but finite risk of having a cardiac event with sexual activity, physicians should discuss with their cardiac patients the risks of sexual activity before prescribing any treatment for ED. In addition, they should evaluate their patients' cardiac status when considering the safety of administering any ED treatment that may have systemic vasodilatory properties and can potentially lower blood pressure. In some cases, exercise treadmill testing may be warranted to determine whether ED patients with coronary artery disease can achieve the physiologic workload (4-6 metabolic equivalents) associated with sexual intercourse.