Meningiomas represent a common class of tumors of the central nervous system. However, the molecular events underlying their formation are poorly understood. Because altered expression of the p53 tumor suppressor gene and the mdm2 proto-oncogene have been demonstrated in a wide variety of tumors, we carried out studies to assess the possible involvement of these two genes in meningioma tumorigenesis. We used Western blot analysis to examine the level of expression of the mdm2 and p53 proteins in a series of sixteen primary meningiomas and four meningioma cell lines. The data obtained from these studies suggest that elevated expression of the p53 or mdm2 protein products does not represent a common event in the development of human meningiomas.