The efficacy of glioma-specific cytotoxic T-lymphocyte for a syngeneic murine malignant glioma (a 20-methylcholanthrene-induced ependymoblastoma, 203-glioma) was investigated. The cytotoxic clone (G-CTLL 1), established and expanded exponentially by T-cell growth factor, has retained target specificity for more than 6 months. In adoptive therapy and Winn assay, the in vivo antitumor activity of G-CTLL 1 was demonstrated against mice inoculated intracranially with 203-glioma cells. The therapeutic effects in adoptive immunotherapy were largely dependent on dose and time of i.v. administration, although the therapy was rather ineffective in condition of increased intracranial pressure due to the tumor growth. The mechanisms responsible for the in vivo protection were probably related to the killing activity of G-CTLL 1 or the tumor-specific production of immune interferon by G-CTLL 1.