Summary: The recent developments in desiccation from the frozen state have been traced and the basic principles described, including initial freezing, methods of carrying out the removal of the water-vapor, degree of vacuum, temperature of desiccation, heating the frozen product without thawing, completeness of desiccation, changes occuring during desiccation and storage, and the type of final container suitable for such products as blood plasma, blood serum, penicillin, and other substances. The factors which control the speed of drying and the ultimate limitations for the most rapid drying cycle are discussed. Much has been learned in relation to these considerations as a result of present-day large-scale production of blood plasma. The manner in which recent developments affect the selection of equipment suitable for use in research laboratories and for the production of blood plasma and other products in hospitals has been discussed.