Summary: We studied 30 patients with postictal psychosis and compared them with 33 patients with acute interictal psychosis and 25 patients with chronic psychosis. All patients had either complex partial seizures (CPS) or EEG temporal epileptogenic foci. Patients with postictal psychosis had a high incidence of psychic auras and nocturnal secondarily generalized seizures. The most striking feature that distinguished postictal psychosis from both acute interictal and chronic psychoses was phenomenological: the relatively frequent occurrence of grandiose delusions as well as religious delusions in the setting of markedly elevated moods and feeling of mystic fusion of the body with the universe. In addition, postictal psychosis exhibited few schizophreniform psychotic traits such as perceptual delusions or voices commenting. Reminiscence, mental diplopia, and a feeling of impending death were also fairly frequent complaints of patients with postictal psychosis. Interictal acute psychosis and chronic epileptic psychosis were psychopathologically similar. Although acute interictal and chronic epileptic psychoses could simulate schizophrenia, postictal psychosis results in a mental state quite different from that of schizophrenic psychosis.