The role of corticosteroids in determining which clinical features of protein-energy malnutrition develop on a deficient diet has been studied by the administration of cortisone acetate to experimentally malnourished rats fed ad lib. on a mixture containing 31 g protein/kg. 2. Daily administration of 1-25 mg cortisone acetate did not affect dietary intake, which remained the same as in saline (9 g sodium chloride/l)-injected controls. Plasma albumin concentrations, however, increased from a low value of 25-7 g/l to 47-2 g/l and this was accompanied by an increase both in liver weight and protein content. On the other hand, the protein content of muscle decreased. 3. These changes in the protein contents of liver and muscle were associated with alterations in the corresponding free amino acid pools. The free amino acid content of muscle generally decreased, but in liver many amino acids were increased.
