In order to study protein-calorie malnutrition two experimental models-calorie deficient and protein deficient models-have been produced in young female rats. When the mean weight of the rats of both models were 48g, the animals were killed. The spleen, liver, kidney, heart and pancreas were studied in relation to weight and nitrogen content, and compared to a control group of the same body weight. In the calorie deficient model only the spleen lost weight, but apparently its composition was unchanged. In the protein deficient model the weight of the liver and pancreas remained similar to those of the control group, but their composition was modified: both organs lost nitiogen and the liver accumulated fat.