The pathogenesis of intraventricular hemorrhage in the newborn includes that of subependymal hemorrhage (SEH), the single most common pathologic alteration seen in the brains of 417 consecutively autopsied infants. A clearly recognizable relationship of SEH to gestational age and clinical status exists in that all SEH occur in premature infants under 2500 g birthweight (although only 56% of all premature infants have SEH) and 95% of SEH occur in infants with the respiratory distress syndrome (although only 60% of infants with the respiratory distress syndrome have SEH). The pathogenesis appears to involve a combination of hypoxia, metabolic acidosis, venous stasis and rupture of the thin-walled veins so prominent in the germinal matrix.