Cerebral ultrasounds were prospectively performed in 100 infants weighing 1,500 gm or less in order to evaluate the prognostic significance of ventricular dilatations and their associated findings. There was no difference in the incidence of ventricular dilatation (24%) between patients with or without periventricular hemorrhage (PVH). Although patients with PVH developed ventricular dilatation significantly earlier than infants without PVH, no differences were observed in severity, location, head circumference growth, or intracranial pressure between the groups. Ventricular dilatation was statistically related to PVH grade III and PVH with parenchymal involvement; grades moderate-to-severe of periventricular echogenicity; and cystic periventricular leukomalacia (PVL). Ventricular dilatation persisted longer than 6 weeks in 61% of infants and had irregular margins in 62%. The latter were significantly related to cystic PVL. Seventy-seven of 100 infants examined were followed until 20 months corrected age. Ventricular dilatation mainly when persistent and with irregular margins was associated with handicaps. We conclude that ventricular dilatation is frequent in very low-birth weight infants. Furthermore, its occurrence may be independent of PVH. Persistent ventricular dilatation with irregular margins, even in its mild forms, suggests a parenchymal lesion and guarded prognosis.