To evaluate the possible role of the autonomic (sympathetic) nervous system function among the patients with primary premature ejaculation (PPE) and determine whether there is an etiological basis for this condition. We performed sympathetic skin response located in the penis (PSSR) in 52 patients with PPE and 46 normally potent men. The latencies and amplitudes of PSSR were measured. The PSSR waveforms were classified into P type and N type according to the waveform characteristics. The waveform distribution in the PPE patients was not statistically different from that in the control group (P=0.609). Mean latency of the PSSR was significantly shorter in the patients than that in the normally potent men (P<0.001). Mean amplitude of the PSSR was significantly greater in patients than that in the normal men (P<0.001). Patients with PPE have hyperactivity of the sympathetic nervous system, which may be another factor involved in the pathological mechanisms of PPE, and the PSSR is an objective test to evaluate patients with PPE.