Erectile Dysfunction usually has a physical cause, such as disease (i.e. Diabetes, Prostate Cancer, Hypertension, etc), injury, or side effects of drugs. Any disorder that causes injury to the nerves or impairs blood flow in the penis has the potential to cause Erectile Dysfunction. Because an erection requires a precise sequence of events, Erectile Dysfunction can occur when any of the events is disrupted. The sequence includes nerve impulses in the brain, spinal column, and area around the penis, and response in muscles, fibrous tissues, veins, and arteries in and near the corpora cavernosa.

Damage to arteries, fibrous tissues, nerves, and smooth muscles, often as a result of a disease, is the most common cause of Erectile Dysfunction. Diseases such as diabetes, hypertension, nerve disease or nerve damage, atherosclerosis, multiple sclerosis, and heart disease account for the majority of Impotent cases. Patients should be thoroughly evaluated for these conditions before they begin any form of treatment for Impotence.

Lifestyle choices that contribute to heart disease and vascular problems also raise the risk of Erectile Dysfunction. Being overweight, smoking, drinking alcohol excessively, and not exercising are possible causes of ED.

Surgery (especially radical prostate and bladder surgery for cancer) can also injure nerves and arteries near the penis, causing ED. Injury to the penis, spinal cord, prostate, bladder, and pelvis can lead to ED by harming nerves, smooth muscles, arteries, and the fibrous tissues of the corpora cavernosa.

In addition, Erectile Dysfunction can be a side effect of many common medicines such as antihistamines, blood pressure medications, appetite suppressants, antidepressants, tranquilizers, and cimetidine (an ulcer drug). Psychological factors such as depression, anxiety, guilt, stress, low self-esteem, and fear of sexual failure can also cause Erectile Dysfunction. Even when Impotence has a physical cause, psychological factors may make the condition worse. Hormonal abnormalities, such as low levels of testosterone, are a less frequent cause of Impotence.