Neutron radiotherapy has been used for patients with malignant gliomas for over a decade; a substantial number of patients have been treated to date. Pathologic analysis of surgical specimens posttreatment and autopsy specimens have documented an increased antitumor effect of neutrons against malignant gliomas, compared with photon irradiation. However, results of neutron trials to date have not shown a survival advantage over conventional radiotherapy for these patients. This article reviews current surgical, radiotherapeutic, and chemotherapeutic approaches to these tumors, the rationale for neutron treatment, and the results of trials of neutron radiotherapy conducted to date for patients with malignant gliomas.