SummaryAn examination for the membrane oxidation as a cause of oxygen poisoning was carried out by using erythrocyte membrane. 1) The addition of erythrocytes obtained from healthy human adults to retinol, dissolved in ethanol, resulted in hemolysis. The hemolysis induced by retinol was inhibited by added α‐tocopheryl acetate to the suspensions. 2) The hemolysis was induced by oxygen bubbling to the erythrocyte suspensions. This hemolysis was also inhibited by α‐tocopheryl acetate, while it was accelerated by a previous treatment of the erythrocytes with retinol in a dose of which hemolysis did not occur. The oxygen‐induced hemolysis accelerated with retinol, was also inhibited by α‐tocopheryl acetate. 3) The treatment of the erythrocyte suspensions with H2O2was carried out in the manner as previously devised by Rose and György, in which the erythrocytes used in this experiment resulted in no hemolysis. When previously treated the erythrocytes with retinol, in a dose of which hemolysis does not occur, hemolysis was induced by adding H2O2in the same manner, while it was inhibited by α‐tocopheryl acetate. When first treated with H2O2and subsequently with retinol, no remarkable hemolysis was observed in the erythrocy