OBJECTIVE: To study the prognostic value of CD133 and HTERT immunoexpression in glioblastoma (GB). GBs are the most frequent primary tumors in the central nervous system. According to the tumor stem cell (TSC) theory, the growth, relapse, and therapeutic resistance of GB would be determined by the presence of a TSC subpopulation. It has been proposed that TSCs can be identified by means of immunohistochemistry for CD133. Furthermore, the percentage of TSCs could be an independent factor of poor prognosis; however, some authors have shown that CD133 expression does not correlate with prognosis. TSCs may express other tumor markers, such as HTERT. STUDY DESIGN: We determined the percentage of CD133+ and HTERT+ tumor cells in 55 GBs using a tissue microarray. The data were correlated with clinical outcome. RESULTS: The increase in CD133 immunoexpression correlated with an increase in survival (p=0.034). HTERT expression alone was not found to be related to poor survival (p=0.385) but was linked to poor prognosis associated with CD133 expression (p=0.04). CONCLUSION: Our results reveal the increase in HTERT expression associated with augmented CD133 immunoexpression as a prognostic factor in GB. © Science Printers and Publishers, Inc.