Erectile dysfunction (ED), or impotence, is the inability to get or keep an erection (hard penis) for enough time to have satisfactory sex. To get and maintain an erection, blood must be able to flow into and stay in the penis. Men commonly have problems with their erections once in a while. But if ED occurs frequently, medical therapy may be helpful. About 30 million men in the United States have ED. It can happen at any age, but is more common in men older than 65. ED is treatable at any age. ED can be a symptom of early blood vessel disease in other locations in the body.