Identification of patients at risk for developing brain tumors is important for the development of preventative strategies. Because individuals with germline p53 mutations may be at increased risk, we examined DNA from brain tumor-derived cell lines and malignant and normal nervous system tissue for p53 gene mutations using the single strand conformation polymorphism assay and direct sequencing of polymerase chain reaction-amplified DNA. We found mutations in the p53 gene in eight of 22 adult glioma tissue specimens and germline mutations in two of these eight patients. In contrast, mutation of the p53 gene was not detectable in either 16 glial tumors occurring in children, glial tumor tissue from three unrelated glioblastoma multiforme patients with a familial history of cancer, or in benign meningiomas. One constitutional p53 mutation was a G to T transversion at codon 154, and the second was a C to T transition at codon 256. Both patients with germline mutations developed glioblastoma multiforme before the age of 31, although the median age for glioma patients is above 50. These findings suggest that p53 germline mutations may identify a subset of young adults predisposed to the development of high-grade astrocytic tumors.