Spinal somatosensory evoked responses to peroneal nerve stimulation were examined in 23 control subjects and 8 patients with pathological lesions of the spinal cord or peripheral nerve. In the control subjects, the response was found as a triphasic potential increasing in latency rostrally at the lumbar spinous recording location. Another negative potential following this triphasic potential appeared at the L1 to T10 spinous recording locations, which might reflect synaptic and/or post-synaptic activity in the spinal cord. This negative response then progressively increased in latency rostrally. The spinal conduction velocity was higher at the upper thoracic leads than at the lower leads. Three patients with spinal cord atrophy showed disappearance of the spinal evoked potential at the spinous recording location corresponding to the pathological lesion. However, since the triphasic potential at the lumbar spinous lead was undetectable in the patients with lesions of the peripheral nerve or cauda equina, the spinal cord function could not be estimated well in these patients.