Because an erection is caused by the penis filling with blood, problems with the blood vessels may result in erection problems (erectile dysfunction). These problems include:

• Hardening of the arteries (atherosclerosis) in the penile arteries, which may block blood flow into the penis or into the arteries that fill the penile arteries.
• Side effects of medications that affect the blood vessels (such as some diuretics or other high blood pressure medications), which may interfere with the filling process.
• Leaking of blood from the spongy chambers (corpora cavernosa) in the penis to the veins that carry blood from the penis. This may lead to the inability to maintain an erection.