Glutamine is a conditionally essential amino acid for low-birth-weight (LBW) and very low-birth-weight (VLBW) infants by virtue of its ability to serve as a primary respiratory fuel for proliferating cells, a carrier of nitrogen between tissues, maintain acid-base balance, promote the growth and integrity of the gastrointestinal tract and promote immunologic responses. While adults can synthesize glutamine in the muscles and brain to meet essential requirements under normal state of health, the LBW and VLBW infants may not be able to do so since the enzymes (glutamine synthetase and glutaminase) activities are low. In addition, these infants are under stress due to conditions like the respiratory distress syndrome, acid-base imbalances, infections, and inadequate immunologic responses. Current amino acid mixtures and formula preparations are inadequate to meet the needs of these infants for this amino acid. Thus supplementation of parenteral and enteral nutrition with glutamine would be beneficial.