Erectile dysfunction (ED) and cardiovascular disease share many of the same risk factors and have some common elements of pathophysiology. Clinically, they often coexist. Another link between the two conditions is that sildenafil, the first oral therapeutic agent effective in treating ED, has been shown to potentiate the hypotensive effects of nitrates, a potentially serious side effect. Nitrates are commonly used in the treatment of coronary artery disease. As such, sildenafil (and, likely, other new phosphodiesterase type 5 [PDE5] inhibitors) is contraindicated in men who use nitrate medications. This article will examine the risk of an acute coronary event during sexual activity, and review an algorithm for evaluating the cardiac risk of a patient with ED. The interaction between PDE5 inhibitors and cardiac medications will be discussed, along with guidelines for using sildenafil in men with cardiac disease.