1. Intracellular energy producing metabolic systems were investigated in erythrocytes before and after insulin stress in 10 control, 10 acute schizophrenic, and 10 chronic schizophrenic male subjects. 2. Following complete clinical study 28 ratings of symptoms and course of illness were made for each subject. 3. Correlation coefficients (r's) were computed between the biochemical and clinical variables. 4. It was found that the primary symptoms were directly related to the failure of mobilization after stress of the compound fructose-1,6-diphosphate. 5. In contrast, the secondary symptoms were not significantly related to biochemical variables. 6. Scores indicating a chronic illness and a poor outcome at followup were found to be directly related to another very important substance in this metabolic scheme. This substance is adenosine triphosphate (ATP). 7. The possible significance of these findings is discussed in relation to a hypothetical serum factor in schizophrenia.