The aim of our study was to examine the cavernous smooth-muscle electric activity in normal and impotent patients as well as in those with (presumably) well-defined neurologic lesions. Single potential analysis of cavernous electric activity (SPACE) was done in 12 consecutive impotent patients, 34 normal patients, and 19 patients referred especially for SPACE. In the normal patients, similar potentials with a mean duration of 9.5 s, a mean amplitude of 153 μV and a mean polyphasity of 8.5 were recorded (cutoff frequencies, 2-2000 Hz), with cutoff frequencies set at 0.5-500 Hz, the mean duration was 12.8 s, amplitude was 444 μV and the mean polyphasity was 13.8 Upper spinal cord lesions showed potentials of long duration as well as whips and bursts. Patients with lower motor-neuron lesions showed either short potentials of high amplitude or potentials of small amplitude. In 49% of the impotent patients, abnormal SPACE was found. Our results suggest that SPACE is a reproducible and minimally invasive method for the diagnosis of autonomic neurogenic impotence. © 1990 Springer-Verlag.