We report nine cases of obstructive or communicating hydrocephalus among 64 infants and children with intraspinal neoplasms. There were three intramedullary, four intradural, and two extradural tumors. Although four patients had papilledema, and five myelograms revealed total block, the total CSF protein level was not always elevated in the fluid above the intraspinal lesion. Analysis of these nine cases permits several different pathogenetic considerations of hydrocephalus associated with intraspinal tumors. The high incidence (14%) of this coexistent syndrome might be a characteristic of intraspinal neoplasms in infants and young children.