Must have recurrent or progressive supratentorial tumor compared with a previous study. Baseline tumor measurements must be determined within 2 weeks prior to study. Stereotaxic biopsy at study entry must confirm the presence of glioma (malignant, unless previously known). Recurrent or progressive tumor must have a solid enhancing region at least 1.0 cm and not more than 6.0 cm in maximum diameter. (One satellite lesion is permitted, if separated by 3 cm or less from the primary mass.)