The response of urea metabolic kinetics, the rate of whole-body protein breakdown, and muscle and skin protein synthesis rates to dietary protein intake (1.15 to 2.92 g/kg/d) was assessed in children with 20% to 40% total body surface area burn injury using a primed continuous infusion of 15N2- urea and L-13C6-phenylalanine. Plasma urea concentration, production, and excretion rates increased with dietary protein intake without evidence of approaching maximum plateau values. There was no consistent evidence of urea recycling in these subjects (urea production = excretion) at any level of protein intake. The rate of appearance (Ra) of phenylalanine (an index of whole-body protein breakdown) and rate of muscle protein synthesis were independent of dietary protein, whereas there was a significant increase in skin protein synthesis with higher protein intake. We conclude that there seems to be little benefit of high protein intake on whole-body protein breakdown end muscle protein synthesis rates in these burn patients, although high-protein diets may enhance wound healing.