The neurodevelopmental outcome at a mean age of 40 months was investigated in 23/25 surviving infants of birth weights less than or equal to 1,000 gm. Eight infants required intubation and assisted ventilation and 17 were not ventilated. One ventilated infant was lost to follow-up and one nonventilated infant was a victim of sudden infant death syndrome at age 6 months. Fifteen (65%) had a good outcome but the differences between ventilated and nonventilated infants were striking. Thirteen (81%) of the nonventilated group were normal, but only two ventilated survivors (28%) were normal (P less than 0.05). Cicatricial retrolental fibroplasia occurred in three (43%) of the ventilated survivors and in none of the nonventilated infants (P less than .02). The requirement for assisted ventilation in these very low-birth-weight infants is associated with significant morbidity. Improvement in outcome may depend as much upon better understanding and management of prenatal events as upon improvements in neonatal care.