Hospital records of 58 premature infants in whom proliferative retrolental fibroplasia (RLF) developed were matched with records of 58 infants without RLF for birth weight, gestational age and duration of O2 therapy. The 2 groups were compared for factors likely to influence tissue delivery of O2 by blood. No significant difference was found in incidence of blood transfusions or exchange transfusions, use of phototherapy or occurrence of acidosis.