Thirteen cases of CNS hemangioblastoma were examined with the immunoperoxidase technique for glial fibrillary acidic protein (GFAP) to determine if there were astrocytic elements among the "stromal cells" of these tumors. In six cases, includinng two leptomeningeal hemangioblastomas, none of the stromal cells were positive on GFAP stain. Seven cases, however, showed variable presence of Gfap positive cells, including clusters of heavily lipidized cells deep within cerebellar hemangioblastomas. These GFAP positive cells were indestinguishable by other stains from interstitial or stromal cells. Thus, it appears that in at least some hemangioblastomas of the CNS parenchyma, a few or many "stromal cells" are lipidized astrocytes. All stromal cells, however, cannot be of astrocytic origin, as proposed by Jakobiec et al. (1976), in view of our six cases where no GFAP-positive cells were found in the tumors. It is suggested that cells identified as "stromal cells" of hemangioblastomas on light microscopy are a heterogeneous group of cells including astroyctic as well as other elements and that they resemble each other on ordinary stains because of the "equalizing effect" of cell lipidization.