Erectile dysfunction (ED) affects nearly two-thirds of men age 50 and older and is an increasingly common presentation in the primary care setting. A thorough evaluation for ED involves a complete medical history, including a review of medical risk factors such as hypertension, diabetes, cardiovascular disease, renal failure, and medications, as well as lifestyle risk factors such as obesity and tobacco, alcohol, and illicit drug use; a detailed sexual history, including assessment of duration of ED, loss of libido, and overall sexual satisfaction; a physical examination; a psychosocial assessment--with particular attention to depressive symptoms; and appropriate laboratory tests. Treatments include medical management of multi-drug regimens, oral therapy, intracavernosal injection, testosterone replacement therapy, vacuum erection devices, and penile prostheses.