Erythrocyte deformability as a clinical indicator of microcirculatory disturbance was determined in the erythrocyte of 25 schizophrenic patients and of 18 normal controls. Schizophrenic patients had significantly lower erythrocyte deformability than did the normal controls (P < 0.001). This result suggests that microcirculation in schizophrenic patients is disturbed, and that this disturbance might be involved in the pathophysiological genesis of schizophrenia.