126 appropriate-for-gestational age neonates born in hospital with birth-weights of 750 g-1500 g were prospectively studied in a randomised trial to determine the effect of intramuscular vitamin E on the frequency and severity of retrolental fibroplasia (RLF). In the 99 who lived for more than one month the frequency of active RLF in the vitamin E and control groups in the nursery (18·8% vs 23·5%) and at discharge (8·3% vs 19·6% was not significantly different. Vitamin E had significantly reduced the severity of RLF at follow-up eye examination 6-33 months after discharge (p<0·01). 3 control infants (760 g, 780 g, 1020 g) were blind in both eyes (grade V cicatricial RLF), whereas the most severe grade of disease in the vitamin E infants was grade II cicatrix. Infants in whom RLF developed were gestationally younger (p = 0·005), required a longer period of mechanical ventilation (p = 0·035), had a greater exposure to oxygen (p = 0·03), and had a greater number of arterial PO₂ values between 75 and 99 mm Hg (p = 0·004). Early administration of vitamin E, while not affecting the frequency of RLF, will significantly reduce its severity and subsequent eye damage, and such treatment is recommended for all low-birth-weight infants of less than 1250 g who require supplementary oxygen.