Erectile dysfunction (ED) is a multisystemic disorder most commonly caused by vascular insufficiency. Because the organic etiologies that cause ED often impact concurrently on other body systems, multiple comorbidities have been noted that occur more frequently among men with ED than among men without ED. This encourages us to consider the presence of ED as a signal of a variety of disorders that have similar etiologies, including psychosocial problems, endocrine imbalances, neurologic disorders, and, most notably, cardiovascular risk factors and/or disease. Evidence is accumulating that ED, especially vasculogenic ED, is a signal for endothelial dysfunction and resultant cardiovascular disease risk. ED may also be a "harbinger" of symptomatic cardiovascular or neurologic diseases. Knowing that a man has ED should encourage further evaluation for these comorbidities, because early detection may allow attenuation of disease risk or actual disease. The best way to perform this evaluation in men with ED needs further study. The role of the presence of ED as a “screening test” for increased cardiovascular disease risk also needs further exploration.