Two-hundred-and-two impotent diabetic patients gave their consent to be investigated. Impotence is linked to diabetes mellitus in 58.9% of patients so all the other etiologies have to be systematically eliminated. Neuropathy or arteriopathy, when isolated, are found with the same frequency, but these 2 etiologies are often associated (47 patients). No statistical difference between IDDM and NIDDM was found. Mercury strain gauge plethysmography and venous occlusion coupled to ECG allows detection of arterial lesions in diabetic impotence. Patients agreed to submit to all of the various therapeutic possibilities. Combination of alpha-blockade and good glycemic control induced the best results.