Studies on the adaptive changes in the membrane hydrolysis and the carbohydrate and protein transport that occur when chickens are fed diets differing quantatively from each other with regard to their contents of major nutrients, yielded the following results: I. By increasing the protein content of the diet (up to 30%), the absorption of carbohydrates and proteins is inhibited. 2. A positive effect of a diet with increased fat content on the digestion of carbohydrates and proteins was observed solely with dietary lipids rich in unsaturated fatty acids (sunflower oil).