Haptoglobin and transferrin types were studied in schizophrenic patients and controls. In the haptoglobin system a significant departure from the Hardy-Weinberg equilibrium with an excess of heterozygotes was found among the patients (p less than 0.01). The distribution of haptoglobin types in the schizophrenic patients was significantly different from that in the controls. The distribution of transferrin types showed a good agreement with the Hardy-Weinberg equilibrium. There was no significant difference between patients and controls with respect to transferrin types.