Erectile dysfunction (ED) refers to an erection dysfunction of the male penis, manifested as an inability to have an erection or having an erection but not hard enough for sexual intercourse in the presence of sexual desire, resulting in sexual intercourse difficulty. A complete inability of the penis to erect is called complete ED, whereas an erection that does not reach sufficient hardness required for sexual intercourse is called incomplete ED. Primary ED refers to cases where ED occurs from the start of development. There are many causes of ED; apart from a few cases caused by organic diseases of the reproductive system, most are psychogenic and constitutional. For men over 50 years old who experience ED, it is mostly due to physiological degenerative changes. In any case of ED, sexual intercourse cannot be completed, which often leads to abnormal male sexual excitement and psychological changes in women, inevitably affecting marital relations and fertility. It may even involve legal issues, so diagnosing ED must be done with caution.