We investigated platelet count, bleeding time, platelet aggregation, prothrombin time, activated partial thromboplastin time, and fibrinogen level in 58 very low-birth-weight infants during the first postnatal day to determine the relationship between hemostatic disorders and intraventricular hemorrhage. Thirty-two of the 58 infants (55%) were found to have periventricular-intraventricular hemorrhage by computerized tomography or autopsy. Nine patients (16%) had subarachnoid hemorrhage only and 17 (29%) had no evidence of intracranial hemorrhage. Infants with IVH had a significantly lower mean platelet count than did infants with no SAH/IVH. However, only five patients with IVH had initial thrombocytopenia. The IVH group had a mean bleeding time which was significantly prolonged compared to that of the group without SAH/IVH. Similarly, patients with IVH had a mean platelet aggregation response which was significantly diminished in comparison to that of patients with no SAH/IVH. Infants with IVH had a significantly longer mean PT than did infants with no SAH/IVH. In addition, babies with IVH had a significantly longer mean APTT compared to that of babies without SAH/IVH. The groups did not differ significantly with respect to fibrinogen levels. Three infants with IVH had disseminated intravascular coagulation in the early neonatal period. These data suggest that disorders of platelet-capillary interaction and defects in the intrinsic and extrinsic coagulation pathways may play important roles in intraventricular hemorrhage in the premature infant.