Intraoperative radiation therapy (IORT) was used as part of the initial therapy for malignant glioma in 32 of 73 patients with histologically verified anaplastic astrocytoma (grade III astrocytoma) and glioblastoma multiforme. The initial treatment for all cases was subtotal or total tumor resection combined with external irradiation and chemotherapy. IORT was performed 1 week after tumor resection, with doses of 10-50 Gy (mean 26.7 Gy) in one session. Fourteen of 32 cases had IORT two times because of tumor recurrence. The IORT patients had survival rates at 24 and 36 months after initial treatment of 57.1 and 33.5% (median survival 26.2 months). The other 41 patients had 23.6 and 13.1% survivals (median survival 20.7 months), which were significantly lower (p<0.01). Tumor recurrence within the original lesion site was suspected because of clinical condition, computed tomography, and magnetic resonance imaging studies in 65.6% of the IORT group (21 cases) 12 months after initial treatment. Twenty cases of death in the IORT group, including five autopsy cases, demonstrated regional tumor recurrence with a high incidence of intraventricular tumor invasion. The authors consider IORT is beneficial for selected malignant glioma patients, including tumor recurrence, because of prolonged survival. (author).