Neonatal alloimmune thrombocytopenia results from platelet-antigen incompatibility between mother and fetus, leading to antibody-mediated destruction of fetal platelets. With a prevalence of 1 in 1000 births, approximately 4000 infants born in the United States each year develop neonatal alloimmune thrombocytopenia. Ten to 20% of affected neonates develop intracranial hemorrhage, with 25 to 50% occurring prenatally. We report three infants who developed prenatal hemorrhage. One died in utero, and the other two had cerebral porencephaly and neurologic deficits. Infants with neonatal alloimmune thrombocytopenia have elevated risks of perinatal death and neurologic complications, including cerebral palsy, hypotonia, cortical blindness, developmental delay, seizures, and psychomotor retardation. We also report our retrospective review of the New England Medical Center neonatal intensive care unit between 1990 and 1999. Using current management guidelines, including treatment of the mother with a weekly infusion of high-dose (1-2 g/kg) intravenous immunoglobulin and/or corticosteroids, all eight infants with neonatal alloimmune thrombocytopenia did well.