To test the hypothesis that nonprotein calorie intake and nitrogen intake are equally important in establishing positive nitrogen balance, weight gain, and serum protein response in the depleted primate treated with total parenteral nutrition (TPN), 10 adult male chair-adapted primates (Macaque fascicularis) were studied. After 10 days of nutritional depletion (nothing by mouth; 5% dextrose with electrolytes administered intravenously) animals were randomized to receive one of four TPN diets for 10 days. The depletion/repletion cycle was repeated, after 1 month of caged free feeding, until all animals had received the four TPN diets. Two levels of nonprotein caloric intake (155% and 100% of primate resting energy expenditure) and two levels of nitrogen intake (200% and 100% of primate nitrogen requirement) were used to make the four different diets. Nitrogen balance (p = 0.01) and serum total iron-binding capacity response (p = 0.02) were significantly influenced by the level of nitrogen intake but not by nonprotein calorie intake, which significantly influenced only weight gain (p = 0.03). Fluid balance was not significantly different for any diet. Fat and protein stores may be selectively repleted in this model by adjusting the nonprotein calorie and nitrogen content of TPN.