Summary Intraventricular hemorrhage was responsible for the deaths of eleven liveborn premature infants; it was the single leading cause of death of previable premature live-born infants. The source of the bleeding was not always demonstrable. In some infants the hemorrhage appeared to arise from the engorged vessels of the choroid plexuses; more frequently it appeared to result from the rupture of one or more subependymal hemorrhages into the ventricular cavity. The stria terminalis thalami was a frequent site of such subependymal hemorrhages. It seems probable that intraventricular hemorrhages cannot be attributed to any single cause but that anoxia, trauma, and the socalled “suction effect” all play a role in their pathogenesis. Prematurity, however, is the one feature common to the vast majority of intraventricular hemorrhages and is certainly the most important factor predisposing to the development of this lesion.