Formalin-fixed, paraffin-embedded surgical specimens from 137 primary central nervous system tumors, including 26 astrocytomas (21 fibrillary, 1 protoplasmic, 1 gemistocytic and 3 pilocytic), 26 anaplastic astrocytomas, 9 glioblastomas, 1 gliosarcoma, 8 oligodendrogliomas, 4 ependymomas, 1 anaplastic ependymoma, 2 subependymomas, 3 paragangliomas, and 57 meningiomas, were immunostained with the CM1 polyclonal (pAb) and the DO-7 monoclonal (mAb) antibodies against the p53 protein, using the streptavidin/peroxidase method. In addition, two series of 17 and 9 medulloblastomas were also immunostained with the above pAb and mAb, respectively. p53 protein expression was observed in 7 fibrillary astrocytomas, 17 anaplastic astrocytomas, 5 glioblastomas, 1 gliosarcoma, 1 oligodendroglioma, 1 anaplastic ependymoma, and 4 meningiomas with the CM1 pAb. An additional 10 cases (i.e., 3 anaplastic astrocytomas and 7 meningiomas) were found to be p53 protein positive with the DO-7 mAb. Of the medulloblastomas, 8 (of the 17) and 4 (of the 9) were found to express p53 protein with CM1 pAb and DO-7 mAb, respectively. Our results indicate that p53 protein is expressed in a number of central nervous system neoplasms, and suggest that in astrocytic tumors a possible association may exist between p53 protein expression and tumor progression through increasing histological grades of malignancy.