A Technique for drying serum proteins from the frozen state has been described by Greaves & Adair (1939). For war requirements the procedure has been to dry in 12 oz. medical flats into each of which is put 200 c.c. of serum. The bottles are then placed in a −20° C. cold room on shelves slightly inclined to the horizontal. The inclination is to allow the maximum quantity of serum to be dried consistent with the exposure of a reasonable surface area from which to dry. This method of freezing produces a wedge-shaped block of serum in the bottle (Fig. 1) and is very efficient. Large amounts of serum for the use of the Army have been dried in this manner by Greaves and his colleagues.