The cytogenesis of so-called hemangioblastoma arising in the central nervous system was investigated using the immunoreactivity to various proteins in cerebellar hemangioblastomas, extracerebellar hemangioblastomas, cerebral hemangiopericytomas, and hemangioendotheliomas, as well as a variety of meningiomas. The antisera used included vimentin, glial fibrillary acidic protein, epithelial membrane antigen, factor VIII-related antigen, and cytokeratin. Lipid-laden cells often encountered in partially degenerated meningiomas revealed almost identical reactivity patterns as the lipid-laden cells, i.e., so-called stroma cells, of hemangioblastomas. The results indicate that the so-called hemangioblastoma of the central nervous system is derived from arachnoid cells in meningotheliomatous meningiomas by way of cellular degeneration.