It is well known that diabetes mellitus is accompanied by complications of sexual dysfunction and it is believed that diabetic neuropathy may cause impotence. In our study, we found that not all the patients who visited our center with the chief complaint of diabetic impotence were suffering from organic impotence, and diabetes mellitus per se served as a means of psychological stress in a substantial number of cases. Probably because no method has been available to provide precise information on the state of the penile-controlling nerves, we found that a larger number of patients than expected were suffering from a vascular disorder.