Purpose: Apoptosis plays a crucial role in normal development and mediates tumor response to chemotherapy. This study investigated the pattern of apoptotic gene expression in brain tumor tissue specimens and cell lines.Materials and Methods: BCL2, BCLXL, BCLXS, and BAX transcripts were amplified using reverse transcriptase polymerase chain reaction in 7 high-grade gliomas (HGGs), 7 ependymomas, and 6 cell lines (2 glioblastomas, 3 medulloblastomas, and 1 supratentorial-primitive neuroectodermal tumor [PNET]). Immunohistochemical staining for BCL2. BCLX, BAX, and p53 was performed in 7 pediatric low-grade gliomas (LGGs) and 7 pediatric HGGs.Results: Six of seven gliomas, all ependymomas, and all glioblastoma and medulloblastoma cell lines expressed BCLXLand BAX. BCL2 expression was only detected in the supratentorial PNET line PFSK. BCLXSwas absent in all tumors. By immunohisto-chemistry, no glial tumors stained positively for BCL2. Similar BAX and BCLX protein expression was observed in LGG and HGG. Three of five glioblastomas showed significant p53 expression.Conclusions: Coexpression of proapoptotic and antiapoptotic genes in human brain tumors supports the hypothesis that the relative expression of competing genes determines apoptotic threshold.