Periventricular-intraventricular hemorrhage is the most important adverse neurologic event of the newborn period. It is very common and can be very severe. Such hemorrhage begins in the germinal matrix but may spread into and throughout the ventricular system. It may be accompanied by hemorrhage within the brin parenchyma. The pathogenesis of periventricular-intraventricular hemorrhage is still imperfectly understood, but relates to the anatomy and physiology of the developing cerebral vasculature and to the biophysical and biochemical environment in which that development proceeds. Periventricular-intraventricular hemorrhage may be marked by a catastrophic clinical deterioration, but is more commonly accompanied by a saltatory progression that may be difficult to detect clinically. Both concomitant neonatal disease and therapeutic intervention for such disease have been implicated in the initiation and exacerbation of periventricular-intraventricular hemorrhage. Real-time ultrasound scanning with portable instruments is now the best procedure for identifying this lesion and for assessing its sequelae. Prognosis relates principally to the severity of the lesion. Early management must be particularly directed to the maintenance of cerebral perfusion. Later management is predominantly the therapy of posthemorrhagic hydrocephalus. There is no currently available therapeutic modality that will prevent progressive posthemorrhagic hydrocephalus.