Fifteen Minor Head Trauma patients were investigated by Brainstem Auditory Evoked Potentials at 10/s and 55/s stimulus rate. The results were compared with those of the same patients at a second examination, two months later, as well as with a matched normal control group. Increasing the stimulus rate in MHT patients caused a significant but reversible delay in the central conduction time. No significant difference was found regarding the interpeak latency differences at a 10/s stimulus rate. The present study suggests that the primary lesion in MHT is ischaemic, affecting synaptic efficiency, and not axonal damage. These findings may be informative on the as yet obscure pathophysiological mechanism of minor head trauma.