1. The Heinz body formation in vitro due to the addition of hydroxylamin hydrochlorate as a blood gift was studied and compared in 71 cases of 22 normal subjects and 49 schizophrenics. 2. The mean value of erythrocytes with Heinz body formation: normal group 94‰ chronic standstill group 146‰; strong excitement and confusion group 211‰, chronic progressive group 213‰; intense deterioration group 304‰. If we suppose the mean value of normal group as 100, so the rate of every schizophrenic group is calculated as follows; chronic standstill group 155; strong excitement and confusion group 224, chronic progressive group 227: intense deterioration group 324. This fact indicates that the erythrocytes of schizophrenic patients are pathological. 3. The resistance of erythrocytes with Heinz body is weaker than that of normal. (by the Ribiere's method). 4. We found that the erythrocytes sedimentation rate in the intense deterioration group accelsrates more than in normal, and that e. s. r. has some relation to Heinz body appearance.