1. The steps in the separation of a factor in the serum of schizophrenic patients have been described.2. This factor has a significant effect on metabolism as measured by lactate/pyruvate ratios in the chicken erythrocyte and the stimulation of energy production by forcing glucose through the Emden-Meyerhof scheme, rather than the hexosemonophosphate shunt.3. This factor is readily affected by pH and temperature, remaining relatively stable between pH 6 and 9 at 4° C. It is probable that this is an alpha globulin or a prosthetic group attached to an alpha globulin.4. The significance of this factor for the schizophrenic illness has not yet been clarified. This may be a substance normally present in the serum of all individuals, but quantitatively elevated in the schizophrenic because of excessive production or its failure to be metabolized or detoxified. On the other hand, this may be a qualitatively abnormal substance characteristic of schizophrenia.5. The possible relationship of this factor to other reported toxic factors in schizophrenia has been discussed.6. Further biochemical studies are in progress to identify the subject, as well as behavioral studies to ascertain its relationship to the production of disturbances in overt behavior.