Objectives: To examine the effect of supplemental glutamine (0.6 g.kg -1.d-1 ) on whole body protein/nitrogen and glutamine kinetics in low birth weight (LBW ) infants receiving parenteral nutrition in the immediate neonatal period. Study design: Premature infants ≤32 weeks gestation with a birth weight from 694 to 1590 g were randomly assigned to either a glutamine supplemented group (n = 10) or to a control group (n = 10). Tracer isotope studies were performed when the i nfants were 6 to 7 days old and had been receiving an amino acid intake of appro ximately 3.0 g.kg -1.d-1 for at least 3 days. Whole body glutamine and nitroge n kinetics were measured with [5-15N]glutamine, [ 2H5]phenylalanine, [1-13C, 1 5N] leucine, [15N2]urea, and GC-mass spectrometry. Results: Supplemental glutam ine was associated with a lower rate of appearance of glutamine (P = .003), phen ylalanine (P = .001), and leucine C (P = .003). There was no significant differe nce in leucine N turnover, urea turnover and plasma cortisol, and C-reactive pr otein levels in the 2 groups. Conclusion: Parenteral glutamine supplement in LBW infants was associated with lower wholebody protein breakdown. Because the decr ease in whole body proteolysis is associated with protein accretion, parenteral glutamine supplement may be beneficial in selected populations of LBW infants. Objectives: To examine the effect of supplemental glutamine (0.6 g.kg -1.d-1) on whole body protein / nitrogen and glutamine kinetics in low birth weight (LBW) infants receiving parenteral nutrition in the immediate neonatal period. Study design: Premature infants ≤ 32 weeks gestation with a birth weight from 694 to 1590 g were randomly assigned to either a glutamine supplemented group (n = 10) or to a control group (n = 10). Tracer isotope studies were performed when the i nfants were Whole body glutamine and nitroge n kinetics were measured with [5-15N] glutamine, [5-15N] glutamine, 2H5] phenylalanine, [1-13C, 15N] leucine, [15N2] urea, and GC-mass spectrometry. Results: Supplemental glutam ine was associated with a lower rate of appearance of glutamine (P = .003), phenylalanine P = .001), and leucine C (P = .003). There was no significant difference in leucine N turnover, urea turnove r and plasma cortisol, and C-reactive protein levels in the 2 groups. Conclusion: Parenteral glutamine supplement in LBW infants was associated with lower whole body protein breakdown. Because the decr ease in whole body proteolysis is associated with protein accretion, parenteral glutamine supplement may be benefited in selected populations of LBW infants.