THE LONG-TERM preservation of blood plasma by freeze-drying has been successfully employed for a number of years, but attempts to prolong the preservation of red blood cells beyond 21 or 28 days have thus far proved unsuccessful. A method which would allow the long-term storage of red blood cells for transfusion purposes would be most desirable for peacetime medicine. The importance of such a method, permitting the stockpiling of red blood cells for the national defense for use in time of national emergency or disaster, is obvious. Our interest in studying red blood cell preservation was originally stimulated by the work of Luyet,1 who has presented evidence that intracellular crystallization of water is perhaps the most damaging of all subzero-temperature effects on living cells. On repeating his work,2 we also succeeded in preventing the hemolysis of red cells caused by ordinary freezing. In addition, we succeeded in maintaining