Human milk (HM) is recognized as the optimal form of nutrition in the newborn period, providing nutrients and a variety of components (minerals, vitamins, enzymes, hormones, growth factors, and immunoglobulins) that are very important for growth and healthy development. In the case of premature (PM) infants, functional and in certain cases, structural development of most organ systems is completed in the weeks following birth. PM infants do not get enough oxygen and may require supplemental oxygen as high as 95%. This high level of inspired oxygen necessary to maintain arterial oxygen tension exposes these infants to more reactive oxygen species (ROS) compared with full term infants. ROS may lead to diseases associated with prematurity, including necrotizing enterocolitis, retinopathy of prematurity, intraventricular-periventricular hemorrhage, and bronchopulmonary dysplasia. There is then a need to reduce oxidative stress or boost antioxidant defenses in these vulnerable infants. Data suggest that HM has unique antioxidant properties that will assist the premature infant in coping with the increased oxidative stress. HM antioxidant components include the enzymes superoxide dismutase for dismutation of superoxide anion, catalase for degradation of hydrogen peroxide (H2O2), glutathione peroxidase for destruction of H2O2 and organic peroxides. Human milk contains other molecules including cysteine, vitamins C and E, which are scavengers of oxygen radicals.