Being unable to have or keep an erection adequate for sexual activity is the defining mark of erectile dysfunction. The problem may manifest itself in several ways. If the dysfunction:
Is transient or appearing only occasionally, the problem is not likely to be serious; all men experience problems with erections at some time in their lives.
Develops gradually and persistently, there is probably a physical cause; this is generally the case with chronic impotence.
Develops abruptly but you still have early-morning erections and are able to have an erection while masturbating, the problem is likely to have a psychological component, perhaps with an underlying physical factor.
Erectile dysfunction persists. Physical causes can be early warning signs of more general, potentially dangerous conditions; for example, narrowing of the penile artery may indicate coronary artery disease or diabetes. For the dysfunction itself, a doctor may suggest a medication that will allow for normal erections or might advise the use of a mechanical device or penile injection therapy. But the underlying medical condition must be addressed and treated.
Erection problems are associated with pain or penile curvature (a condition called Peyronie's disease).