This study was undertaken to identify the normal somatosensory evoked potential pattern from stimulation of the common peroneal nerve in order to provide basic data for clinical use in diagnosis and management of patients with spinal cord lesions. Thirty-four adult volunteers, free of neurological disease, and 12 patients were tested. The recording technique is described and is similar to that reported by Perot. The primary evoked response (P1) was easily visualized in 88% of the recordings from normal subjects. The peak latency of the primary response was 38.9 msec, and the deflection was positive. A vertex potential (P4) was a relatively consistent peak that appeared at approximately 240 msec in 78% of the subjects. Additional components of the waveform are also described and are compared to previous studies. Clinically, the presence of primary response seems to correlate with a favorable neurological outcome, and recovery of the primary response may precede major clinical improvement. The literature is reviewed and results compared to the current study.