Premature infants have a lower selenium concentration in serum than full-term infants and children. The selenium concentration goes down quickly in infants treated for respiratory distress syndrome without supplementation. One premature infant with bronchopulmonary dysplasia had persistently low concentrations of selenium. Vitamin E supplements did not affect the serum selenium concentration in healthy premature infants. Supplementation with 3 <i>µ</i>g/kg of selenium in parenteral fluids prevented the fall in the concentration seen in other infants not supplemented. Premature infants and especially those treated withoxygen may warrant selenium supplementation to the parenteral nutrition solution. Vitamin E supplements alone are apparently not sufficient to prevent selenium deficiency and potential oxygen toxicity.