ABSTRACT. In 20 healthy premature infants, 10 of whom were administered a total dose of 120 mg/kg vitamin E intramuscularly during the first 13 days after birth, polymorphonuclear leukocyte (PMN) bactericidal activity, frequency and index of phagocytosis, NBT reduction, random movement, chemotaxis and metabolic activity were evaluated within the first 48 hours and again at 5, 14 and 30 days of age. PMN function was also assessed in 30 adult controls. In the treated and untreated infants no differences were found in PMN function before treatment with vitamin E; however phagocytosis, bactericidal activity and chemotaxis were significantly lower than in the adult controls. At 5 days of age, in the untreated infants both index and frequency of phagocytosis remained low but in the treated groups increased significantly. At 14 and 30 days phagocytosis was normal in both treated and untreated infants. No differences were found in the bactericidal activity, NBT reduction, random movement, chemotaxis or metabolic activity of the treated and untreated infants at the ages studied. This preliminary report suggests that vitamin E may be used in premature newborns for accelerating normalization of phagocytic function in the neonatal period.