The evolving techniques of motor evoked potential (MEP) monitoring are reviewed here with reference to their application in clinical and experimental CNS trauma, and with particular relevance to spinal cord injury. Transcutaneous electrical stimulation of the motor cortex for analysis of descending pathways has been developed over the past 6 years in a number of centers. It has now been greatly augmented by the introduction of magnetic stimulation technology. The MEP offers a valuable insight into the physiological status of motor tracts within the spinal cord and is applicable to conscious patients, intraoperative monitoring, and animal studies. It is seen as complementary to somatosensory evoked potential monitoring rather than an alternative or replacement for it. The chief limitations of the technique, common to all evoked potential methods, are the restricted information content, and the need for rigorous electrophysiological interpretation of the resulting signals, if meaningful diagnostic data are to be extracted.