This immunohistochemical, neuropathological study was performed on the ventricular wall of the brainstem in children with fetal and neonatal posthemorrhagic and congenital hydrocephalus. In posthemorrhagic hydrocephalus (PHH), hemosiderin deposits, nodular gliosis, ependymal cell loss and subependymal rosette formation developed subventricularly after 2 weeks of age. Ferritin-positive reactive microglia were well stained until about 2 weeks of age and thereafter diminished as reactive astrocytosis occurred. In congenital hydrocephalus (CH), the damage to the ventricular wall was less than in PHH at all ages and was associated with only mild astrogliosis. These differences in the neuropathological findings of periventricular regions, consisting mainly of glial reactions between PHH and CH, are due to differences in pathophysiology, and the timing of the insult in both conditions. The differences may be due to the effects of intraventricular hemorrhage and/or rapidly increased intracranial pressure in PHH. These results may have implications for the neurological prognosis in children with PHH.