The importance of glutamine as a fuel (substrate) for intestinal epithelial cells and lymphocytes has been increasingly recognized. Glutamine may be a conditionally essential amino acid for premature infants, yet it is not supplied by currently available amino acid solutions. The few trials done in premature neonates have demonstrated safety and potential benefit of parenteral glutamine supplementation as a promising therapy. Conversely, no studies to date have demonstrted any significant toxicity with glutamine supplemented parenteral nutrition. This large multicenter randomized clinical trial will attempt to assess the efficacy of supplemental glutamine on reducing the incidence of mortality or late-onset sepsis in extremely low birth weight infants. (This is an NICHD muticenter study.)