Erectile dysfunction is defined as the inability to obtain or maintain an erection, It can occur in males at any age, but becomes more common as men get older. It can be caused by an injury to nerves or loss of blood supply to the penis, or by other underlying conditions such as diabetes, improper blood pressure, high cholesterol, and atherosclerosis. Certain drugs can also result in erectile dysfunction. Treatment options were limited until the 1990s when Viagra became the treatment drug of choice. See also Impotence