40 patients in acute posttraumatic coma were assessed with help of 3 electrophysiological methods: short latency somatosensory evoked potentials (SEPs), brainstem auditory evoked potentials (BAEPs) and EEG, the results of which were compared with clinical outcome 3 months after the head injury (Fisher's exact probability test). SEPs proved to be the most reliable method for prognostic evaluation of these patients (p less than 0.001), followed by the EEG (p less than 0.002), the prognostic relevance of which, however, is limited by the use of narcotic drugs (barbiturates). BAEPs are less useful for the evaluation of these patients (p less than 0.01), which may be due to traumatic lesions of the cochlea, or even more often, to blood clots in the external ear canal, leading to conducting hearing loss. Conversely, the short axons of the auditory structures of the brainstem appear to be less susceptible to shearing forces of the primary mechanical impact, than the comparatively widely extended thalamocortical connections of the afferent somatosensory system.