Single-unit activity in the cerebellum of awake cats was recorded during generalized paroxysmal activity induced by intramuscular administration of penicillin. Cortical paroxysmal events could provoke changes in the gross electrical activity of the cerebellum that were associated with altered neuronal activity. Coincident with the cerebellar paroxysms, Purkinje cells showed one of two types of activity: an increase in simple spike discharges associated with the surface-negative phase of the paroxysm, or an excitatory-inhibitory sequence. Normal firing patterns resumed quickly after cessation of the paroxysmal discharges. The cerebellum thus appears to be markedly involved in this model of generalized epilepsy and may be involved in its physiopathogenesis. © 1977.