Electrophysiological monitoring of the activity of the penile sympathetic skin responses (PSSR) in healthy men and patients with erectile dysfunction (ED). Methods: PSSR were recorded from the skin of penis with disk electrodes at the time of electric stimulation of left median nerves. Results: PSSR were recorded from all the healthy men and almost all the patients. In healthy men the latency of P0, the latency of N1, the duration of N1 and the amplitude of N1 were 1249 ± 111 ms, 2239 ± 286 ms, 1832 ± 505 ms and 470 μV (median), respectively. In ED patients the latency of P0, the latency of N1, the duration of N1 and the amplitude of N1 were 1467 ± 183 ms ( P ＜ 0.01), 2561±453 ms (P ＜0.05), 2560±861 ms (P ＜0.01) and 91 μV (P ＜0.01), respectively. The normal latency of P0 was less than 1471 ms. The normal amplitude of N1 was more than 235 μV. According to this normal value, of 20 patients 11 showed longer latency of P0, and 14 showed lower amplitude of N1 as compared with those of normal subjects.Conclusion: PSSR can be used as an electrophysiological method in assisting the diagnosis of ED.