Between January 1977 and September 1980, 166 patients were entered on a RTOG protocol comparing neutron-boost radiotherapy with standard treatment for patients with glioblastomas. Eighty-three patients were randomized to receive a neutron boost and 83 to receive a photon boost after 50 Gy photon, whole-brain irradiation. Of these, six were ineligible and two were cancelled, leaving 158 patients available for analysis. The median survival for the neutron-boost group was 9.8 months, compared to 8.6 months for the photon-boost group. The difference is not statistically significant. Autopsies revealed actively growing persistent tumor in all photon-treated patients compared to no evidence of actively growing tumor in the majority of neutron-treated patients.