We analyzed the clinical efficacy and toxicity of concurrent therapy as a first line modality for malignant glioma patients. From 1998 to 2004, 39 patients, 22 with glioblastoma (GM), nine with anaplastic astrocytoma (AA), 7 with anaplastic oligodendroglioma (AO) and 1 with anaplastic oligodendro-astrocytoma (AOA) were enrolled in this study. The median age was 46.2 years (range 8-67). Both external involved field radiotherapy and chemotherapy, composed of CCNU (75-110 mg/m(2)), procarbazine (60 mg/m(2)) and vincristine (1.4 mg/m(2)), were started simultaneously two weeks after surgery. The median progression-free survival time for the GM, AA, and AO patients was 6, 26, and 31 months, respectively. The median survival of the patients with GM and AA was 27 and 41 months. The two-year survival rate of the GM and AA patients was 50.4 and 66.7%, respectively. Grade III/IV hematological toxicity was reduced from 25.6 to 13% after reduction of the dose of CCNU (75 mg/m(2)). Radiation necrosis was confirmed by pathologic examination in four patients (10.3%). The median interval from the completion of radiotherapy to the diagnosis of necrosis was 19 weeks. Modified concurrent chemoradiotherapy may be a feasible option for treating malignant glioma with acceptable toxicity.