We studied the effect of vitamin E on the development of bronchopulmonary dysplasis in neonates with respiratory-distress syndrome. Twenty infants received vitamin E administered intramuscularly during the acute phase of the syndrome, and 20 infants served as controls. Administration of vitamin E significantly increased the serum vitamin E concentration. Nine vitamin-treated and 13 control patients required supplemental oxygen for longer than 250 hours; all were treated with positive-pressure ventilation and endotracheal continuous distending airway pressure. Six of those 13 controls had x-ray changes consistent with bronchopulmonary dysplasia, and four died. None of the nine vitamin-treated patients had changes characteristic of bronchopulmonary dysplasia (P = 0.046), and all survived. Administration of vitamin E during the acute phase of the respiratory-distress syndrome appears to modify the development of bronchopulmonary dysplasis.