1. Research appearing since 1920 on abnormalities in the results of common laboratory procedures applied to patients with affective and schizophrenic psychoses has been reviewed with the assumption that such abnormalities are occasioned by a variety of factors including the effect of emotion and mood upon various body systems, changes in dietary habits, and changes in activity.2. It is felt that such information will be helpful in following the course of therapy on patients with these conditions, will assist in differentiating findings due to these psychoses from those of intercurrent disease, and will prevent certain laboratory results from misleading physicians who encounter patients with undiagnosed, early, or borderline affective or schizophrenic psychoses in general hospitals, clinics and private practice.3. Special attention has been given to abnormalities of the glucose tolerance curve, blood cholesterol level, serum calcium level, leukocyte count, permeability quotient, liver function tests, and basal metabolic rate in these psychoses. In addition, numerous other laboratory tests are discussed.