Penile erection is a complex hydraulic process, in which the cardiovascular system (CVS) plays a central role. Erectile dysfunction (ED) is the inability to achieve, and/or maintain penile erection sufficient for satisfactory sexual intercourse, and was previously regarded as part of aging. It is associated with certain diseases and life style habits with a cause-effect relationship, including diabetes mellitus, hypertension, dyslipidemia, and cigarette smoking. Through atherosclerotic narrowing, these diseases may cause coronary artery disease (CAD) and ED, with ED featuring earlier due to the small size of the pudendal artery. The common denominator in ED and CAD is endothelial dysfunction. Men presenting with ED should be evaluated for CVS risk factors, as there is mounting evidence that ED is a sentinel event for CAD. The treatment of men with CAD and concomitant ED should be individualized, and undertaken jointly by the managing physician and urologist.