Experiments were performed on chronically prepared cats to determine the effect of cerebellar stimulation on generalized "centrencephalic" epilepsy produced by large intramuscular injections of penicillin. Diffuse epileptiform activity developed approximately 1 hr after penicillin injection. Recording of electrical activity from cerebellar structures indicated prominent paroxysmal activity to be present during cortical epileptiform activity. Cerebellar stimulation at 10 and 100 Hz resulted in prompt and significant decrease in the number and amplitude of paroxysmal events. Mesencephalic reticular formation stimulation also reduced the amount of abnormal activity, but, in contrast to cerebellar stimulation, this reduction did not outlast the stimulus period. Inhibition by cerebellar stimulation is attributed to activation of fastigial bulbar pathways. © 1976.