For an investigation of the clinical sequelae of parenteral lipid infusions during the first week of life, 42 neonates (less than 1750 gm birth weight) were randomly assigned to receive parenteral alimentation with (IL) (Vitrum) or without a parenteral lipid infusion (NL) for 5 days. Follow-up clinical status was monitored and compared, and plasma prostaglandin levels were analyzed. Chronic lung disease was increased in duration and tended to be more severe after lipid administration. The number of days of mechanical ventilation (37 +/- 35 vs 21 +/- 18) and supplemental oxygen therapy (51 +/- 39 vs 28 +/- 23) was significantly increased in the IL group. Five IL infants developed stage 3 bronchopulmonary dysplasia, in comparison with none of the NL infants. Seven IL infants were discharged on a regimen of supplemental oxygen therapy versus none of the NL infants. Thromboxane B2 levels were significantly increased in the babies receiving Vitrum. We conclude that early administration of Vitrum in the premature neonate is associated with increased respiratory difficulty in the ensuing weeks of life.