Introduction In a previous study1 12 chronic schizophrenic patients were compared to 7 and, at a later time, to 13 additional normal control volunteers as to the changes in the concentration of plasma free fatty acid (FFA) and blood glucose which followed the intramuscular administration of insulin. In both phases of the previous study, 6 of the 12 schizophrenic patients showed abnormality of FFA response to insulin but no obvious abnormality of glucose response. However, the schizophrenic and normal groups were not strictly comparable. The normal patient group was on the average younger and lighter in weight than the schizophrenic patient group. Furthermore, previous investigators have noted delayed and decreased response of blood glucose to injected insulin in schizophrenic patients.2-6 In this present study, glucose and FFA sensitivity to insulin are evaluated more fully within the same group of chronic schizophrenic patients by