In a randomized prospective study, we investigated the effect of antenatal phenobarbital on neonatal intraventricular hemorrhage in 39 women destined to deliver babies of less than 32 weeks of gestation. The treatment group received an intravenous loading dose of 700 mg of phenobarbital, followed by a daily maintenance dose until delivery. The newborns were treated with phenobarbital for the first 96 h. Ultrasound examinations of the infants' heads were performed. Intraventricular hemorrhage was significantly less frequent in the treated group: 2 of 21 (9.5%) versus 9 of 18 (50%; p less than 0.006). Moreover no severe hemorrhage (grade 3-4) occurred in the treated babies: 0 of 21 versus 5 of 18 (27.7%; p less than 0.01).