In 1986, a pilot Phase I/II project was initiated using Iodine-125 labeled anti-epidermal growth factor receptor-425 in the treatment of patients with recurrent glioblastoma multiforme of the brain. The monoclonal antibody was administered intra-arterially by the internal carotid arterial system or the vertebral arterial system depending upon the blood supply to the tumor. The treatment program was repeated at intervals for two or three times. Demonstrated was the intense localization of the monoclonal antibody in the brain tumor prior to therapy using Indium-111 labeled anti-epidermal growth factor receptor-425. This localization was demonstrated prior to any therapy as well as after failure from primary radiation therapy with or without concomitant chemotherapy. To date, 15 patients have been treated following recurrence of their glioma (1/15 metastatic adenocarcinoma) with the monoclonal antibody labeled with Iodine-125. Of the 15 patients, there has been one surgically documented complete response, two partial responders, and five patients with stable disease. The results indicate the potential activity of this radiolabeled monoclonal antibody and have prompted continued accession of patients into a Phase II study as a part of the primary treatment regimen (surgery, radiation therapy with or without chemotherapy) followed by administration of the Iodine-125 labeled anti-epidermal growth factor receptor-425.