Surgically excised intracranial hemangiopericytomas from three patients were cultured in vitro and they were examined by immunohistochemistry and electron microscopy to trace the origin of intracranial hemangiopericytomas compared to meningiomas. In all of the three hemangiopericytoma cell cultures, the matrix stained positively for vimentin and desmin. Two stained positive for actin and laminin. Cultured meningioma cells were positive in vimentin staining but negative in others. Hemangiopericytomas continued to have prominent intracytoplasmic intermediate filaments, microfilaments forming dense bodies and pinocytotic vesicles. Reconstruction of only a few cell junctions of zonula adherens type after subcultivation were observed in hemangiopericytoma, while there were neither whorl formations nor cell junctions found, such as desmosomes and junctional complexes, which are common in cultured meningioma cells. These results suggest that intracranial hemangiopericytoma has something in common with muscle cell, endothelial cell and fibroblast which form the vascular and perivascular tissues, and it is distinguishable from meningioma.