The present study deals with the diabetic neuropathies prevailing in men. In this investigation 100 insulin-dependent diabetes mellitus (IDDM) and 3 14 non-insulin-dependent diabetes mellitus (NIDDM) patients with and without an objective evidence of neuropathy, having an age span in between 15 and 60 years and a duration of diabetes distributed over 1-33 years, were included along with their agematched nondiabetic controls. The diabetic subjects were evaluated for the induction of erectile responses. Investigation of induction of erectile responses to erotic stimulation by film and fantasy revealed striking results in diabetic patients with established neuropathy. Both IDDM and NIDDM patients with neuropathy exhibited a highly significant decrease (P < .0005) in penile diameter and length, penile arterial pulse amplitude, both systolic and diastolic blood pressures, and heart rate compared to controls of the same age group. However, both IDDM and NIDDM patients without neuropathy showed a nonsignificant difference in the above-mentioned parameters compared to control subjects. A nonsignificant association of induction of erectile responses to erotic stimulations among IDDM and NIDDM patients with and without neuropathy was also observed, suggesting that impotence and altered erectile responses are likely to be associated with an increased frequency to autonomic neuropathy in these patients irrespective of their type of diabetes.