Summary:The use of intraoperative neurophysiologic monitoring of cranial nerves is reviewed. Over the past 15 years, intraoperative monitoring has been used increasingly during various operations that may involve surgical injuries to cranial nerves. Such monitoring relies on the assumption that some neuroelectric potentials change as a result of injury to a specific cranial nerve and that the risk of permanent injury can be reduced by reversing the surgical manipulation that caused the change in the recorded potentials. It is shown that such monitoring can be performed using methods similar to those used in routine clinical testing and in the physiological laboratory for many years. Although it has been difficult to prove the efficacy of such intraoperative monitoring, except for that of a few cases, such monitoring is generally regarded to be beneficial in helping to decrease the risk of permanent postoperative deficits. In specific operations these electrophysiological methods can aid the surgeon in the operation in various ways, and in many situations it provides a feeling of security for the surgeon. Communication between the monitoring team and the surgeon as well as the anesthesiologist is essential for the success of intraoperative neurophysiological monitoring.