Glioblastoma (GB) is a highly infiltrative tumor recurring in 90% of cases within a few centimeters of the resection cavity, even in cases of complete tumor resection and adjuvant chemo/radiotherapy. This observation highlights the importance of understanding this special zone of brain tissue surrounding the tumor. It is becoming clear that the nonneoplastic stromal compartment of most solid cancers plays an active role in tumor proliferation, invasion, and metastasis. Very little information, other than that concerning angiogenesis and immune cells, has been collected for stromal cells from GB. As part of a translational research program, we have isolated a new stromal cell population surrounding GB by computer-guided stereotaxic biopsies and primary culture. We named these cells GB-associated stromal cells (GASCs). GASCs are diploid, do not display the genomic alterations typical of GB cells, and have phenotypic and functional properties in common with the cancer-associated fibroblasts (CAFs) described in the stroma of carcinomas. In particular, GASCs express markers associated with CAFs such as fibroblast surface protein, alpha-smooth muscle actin (α-SMA), and platelet-derived growth factor receptor-beta (PDGFRβ). Furthermore, GASCs have a molecular expression profile different from that of control stromal cells derived from non-GB peripheral brain tissues. GASCs were also found to have tumor-promoting effects on glioma cells in vitro and in vivo. The isolation of GASCs in a tumor of neuroepithelial origin was unexpected, and further studies are required to determine their potential as a target for antiglioma treatment.