The effect of growth hormone on protein kinetics was assessed in burned patients during the hyperdynamic phase using N15 lysine and balance data across the leg. Levels of resting energy expenditure and cardiac index were comparably elevated in all patients, but leg blood flow was greater in the patients receiving growth hormone. Growth hormone therapy (0.2 mg/kg per day) significantly stimulated protein synthesis in the whole body and in the studied leg. A hyperinsulinemic clamp, which raised the insulin concentration to more than 1435 pmol/L of blood, caused comparable stimulation of leg protein synthesis in patients not receiving growth hormone, but did not further increase protein synthesis in the growth hormone-treated patients. These results suggest that administration of exogenous growth hormone may limit the peripheral protein wasting in severely injured patients by a mechanism similar to that of insulin.