The intravenous clonazepam effect on the interictal EEG of epileptics was studied in 40 patients. In 29 patients (72.5 per cent) the peak potential activity showed a decrease, in 7 patients (17.5 per cent) it remained uninfluenced, and 4 patients (10 per cent) showed an increase. Statistical differences in the effects between the individual forms of the epilepsy could not be secured. There appears to be a tendency towards a better influence on generalised peak potentials as compared to the focal ones. Some focal findings became more pronounced by the action of clonazepam.