The author studied the hemolytic action of chlorpromazine on rabbit erythrocytes and obtained the following results: 1. Chlorpromazine caused hemolysis in vitro. The hemolytic action of chlorpromazine was milder than that of saponin(Colleman and Bell Co) 2. Cholesterol had no marked effect on chlorpromazine hemolysis. 3. Dextrose, albumin and blood plasma protected erythrocytes against chlorpromazine hemolysis. 4. The mechanism of chlorpromazine hemolysis seemed to be different from that of saponin hemolysis. 5. Chlorpromazine increased tile osmotic fragility of rabbit erythrocytes. 6. The intravenous injection of chlorpromazine caused hemolysis in vivo.