Epidemiologic studies are descriptive and analytical. The prevalence of erectile dysfunction in various community studies has varied from as low of 7% to as high as 52%. The prevalence of erectile dysfunction increases with age. Incidence data are scarce but a recent study of white males in the United States described an incidence of 26 cases per 1000 man-years. Risk factors for erectile dysfunction include certain medications, such as cardiovascular medications and psychotropic drugs, and chronic diseases, particularly neurologic diseases and diabetes mellitus.