The survival rate for patients with malignant gliomas is poor. We describe the results of a prospective study using concomitant chemoradiotherapy, neutron boost, and adjuvant chemotherapy for patients with malignant gliomas. Forty-two patients with anaplastic astrocytoma (AA) and glioblastoma multiforme (GBM) were treated with postoperative photon radiation 45 Gy/25 fraction (fxs) with concomitant continuous intravenous infusion of 5-fluorouracil at 300 mg/m2/day×5 days and hydroxyurea 0.5 g orally every 12 hr for 6 days for 5 consecutive weeks, followed by a neutron boost of 450 N cGy/6 fxs delivered twice weekly. Adjuvant chemotherapy with procarbazine, CCNU, and vincristine (PCV) was given up to 1 year or until tumor progression. Thirty-four patients (81%) had GBM and 8 patients (19%) had AA. Sixteen patients (38%) were ineligible for the neutron boost because of large tumors or poor performance status and instead received a photon boost with concomitant chemotherapy for a total dose of 60–65 Gy to the tumor. The overall median survival is 68 weeks at a median follow-up of 203 weeks (range 166–302 weeks for the 11 patients remaining alive); 7/8 patients with AA are alive, 2 of these with progressive disease. For AA the median survival is not reached at a median follow-up of 203 weeks (range 166–302 weeks for the 7 patients alive with AA). Time to tumor progression for the 1 dead patient with AA was 35 weeks and the other 2 patients failed at 171 weeks and 179 weeks following treatment. The median survival for the 34 patients with GBM was 62 weeks; 4/34 patients with GBM are alive at 285, 238, 216, and 206 weeks. Multivariate survival analysis in the 34 patients with GBM revealed age and Karnofsky performance status as important prognostic factors. Extent of surgery and neutrons did not affect survival. Concomitant chemoradiotherapy was well tolerated by all patients. The only toxicities observed were mucositis×grade II in 3 patients (7%) and mild myelosuppression in 1 patient (2.4%). Adjuvant PCV was well tolerated. Continuous concomitant chemoradiotherapy was well tolerated by all patients with acceptable side effects. The survival rate for the patients with GBM suggests no significant impact on the prognosis for these patients. Patients with AA did well; however, the patient numbers are small.