Interleukin-6 (IL-6) is frequently produced in gliomas and has been implicated as a mediator of growth control in several human neoplasms. In this study, IL-6 expression was examined in 11 surgically resected glioblastomas and a cell line U87MG by immunohistochemical staining and quantitative real-time RT-PCR. The relationships between IL-6 expression level and clinical presentation, survival, imaging findings, age and preoperative Karnofsky performance status were analyzed. The median survival times were 16 months in patients with negative IL-6 expression and 7 months in those with positive IL-6 expression (P = 0.075). Three of these patients with a relatively longer survival time (> 1 year) did not express IL-6 in the tumor. Relatively more severe peri-focal edema on imaging was also noted in the glioblastomas with IL-6 expression. IL-6 was also found in the cytoplasm of endothelial cells of newly formed vessels and infiltrating inflammatory cells. These preliminary results implicate IL-6 expression as a possible prognostic indicator in glioblastoma. This cytokine may also play a role in tissue edema, angiogenesis and inflammation of this tumor, but whether IL-6 expression promotes malignancy is uncertain.