Glioblastoma multiforme (GBM) represents the most devastating adult brain tumor. GBM follows a hierarchical development in oncogenesis, with a sub-population of cells - brain tumor stem cells (BTSCs), exhibiting tumor-initiating potential. BTSCs possess extensive self-renewal capability and can repopulate the entire tumor mass. They are resistant to conventional therapies, suggesting that they are the likely candidates of tumor recurrence. Their eradication is thus important for an effective cure. Previous works showed that human-derived BTSCs could be stably maintained for 10-15 passages in serum-free condition, and gene expression and karyotypic hallmarks similar to the primary tumors were preserved. However, primary cells have been shown to sustain additional karyotypic aberrations owing to the harsh conditions of extended in vitro serial passage. Several investigators have proposed passaging these cells in xenograft models. A limitation of such an approach is the inability to return to identical passages for experimental repetitions, or the unavailability of suitably-aged mice for implantation. We have devised a method to cryopreserve BTSCs and that important characteristics were maintained, establishing a repository for drug screening endeavors.