One objection to using cell cultures for studying the proliferation of tumors is the potential for phenotypic changes that may occur in vitro. Here, we compared the antigen pattern expression of cultured meningioma cells with that of the primary tumor. Cell cultures established from 9 intracranial meningiomas and deparaffinized sections of the resected tumors were analyzed for immunophenotyping with the following antibodies: vimentin, cytokeratin, epithelial membrane antigen, S-100, neuron-specific enolase, synaptophisin, factor VIII-related antigen, CD4, CD31, CD34, CD45RB, CD68-PGM1, CD68-KP, and myeloid/histiocyte antigen (MAC387). Overall, the cultured meningioma cells retained the main feature of the primary tumor, being positive both for mesenchymal antigens and for epithelial antigens. Interestingly, the cultured meningioma cells abundantly expressed the CD68 antigens at early passage. The CD68 antigens, which are normally found on hematopoietic cells like macrophages and monocytes, were not detectable on meningioma cells in situ. Our results show that phenotypic changes on human meningioma cells may occur in vitro. This phenomenon suggests caution when transposing the in vitro results to the in vivo condition.