The results presented in this work show that in the spray freeze drying process substantial reductions in the duration of the pri- mary and secondary drying stages can be realized, when stratified packed beds are employed which have a structure as that depicted in Fig. 3. The stratified packed beds provide larger average overall heat and mass transfer rates than those obtained by a spray freeze drying process which uses a packed bed formed by particles all having the same particle diameter and the total amount of solids in the single packed bed is the same as that in the stratified packed bed. The larger average overall heat and mass transfer rates real- ized in stratified packed beds, provide higher drying rates and reduce the duration and maximum thickness of the secondary dried layer, and, thus, the deleterious effects of the secondary dried layer on the transfer of heat from the lower heating plate to the partially frozen and fully frozen particles of region III (as per Fig. 2) during the primary drying stage, are significantly decreased.