The serum of patients with functional psychoses contains abnormal globulins.1As a possible explanation of this I have previously suggested that an autoimmune mechanism might be involved in the pathogenetic chain of events leading to some functional psychoses.1-3The studies reported here demonstrate, in psychotic patients' sera, factors which react with a constituent of brain. Methods I.Serum Collection A. Control Subjects: Sera of 85 blood donors were obtained. B. Patients: 1. Blood was drawn from 72 patients with acute mental disturbances within 24 hours of their admission to this Institute and before administration of phenothiazine, monoamine oxidase inhibitor, or electroshock therapy here; only 14 (19%) had had such treatment during the 3 months before admission. The various so-called functional psychiatric diagnoses ranged from psychogenic headaches to acute catatonic schizophrenia; about 75% had a major functional psychosis. All patients with