Twenty-six orthopedic and 8 neurosurgical patients undergoing spine surgery had spinal cord monitoring before, during, and after operation using somatosensory, averaged cortical evoked responses. Although no inherent risks were apparent in the technical application of this form of spinal cord monitoring, there are limitations that have yet to be evaluated. Classically, somatosensory evoked responses have been considered a function of the posterior columns; however, the results of these studies indicate that more than the function of the dorsal columns alone can be evaluated with this technique. In addition, much remains to be learned regarding the changes in signals noted and the corresponding clinical conditions. Techniques more sophisticated than visual evaluation of response patterns must be established and more sophisticated methods of analysis must be developed. Despite the need for more knowledge of the nature of this system and the correlation between evoked responses and clinical conditions, the system has proved to be effective and to have great potential for improving spine and spinal cord surgery.