Increases in liver and lung alpha-tocopherol (vitamin E) content occur concurrent with birth and the onset of suckling in the newborn rat and are prevented by denying pups access to dams. Liver alpha-tocopherol concentration peaks at 24 hours of age and then declines, whereas the lung concentration of alpha-tocopherol continues to increase in the early neonatal period. These tissue changes are not reflected by changes in the blood alpha-tocopherol concentration. Significant increases in lung alpha-tocopherol result from administering alpha-tocopherol (100 mg/kg body weight, sc) on days 0, 2, and 4 of age. Studies of lung alpha-tocopherol concentrations in infants with varying histories of alpha-tocopherol exposure confirm the findings in the rat, and suggest that increases in lung alpha-tocopherol concentration result from administration of alpha-tocopherol in the immediate newborn period. Studies of alpha-tocopherol values in alpha-tocopherol-treated and control newborn rats reveal no significant changes in lung tocopherol concentration resulting from exposure to hyperoxia.