The treatment of primary intracranial tumors gained the attention of the earliest pioneers in neurological surgery. Despite the efforts of more than three-quarters of a century, therapeutic results remain far from satisfactory. The principal methods of therapy available are still only surgery, radiation, or a combination of the two. Some probing with chemotherapy has been instituted and is of interest, but at present this is primarily investigative. Tissue immunity, as far as application to the treatment of brain tumors is concerned, has received practically no attention. This situation and the magnitude of the problem of brain tumors prompted an evaluation of results obtained with available therapeutic methods. This study includes all the patients who have come under the care of members of the Faculties in Neurological Surgery and in Radiation Therapy at the University of California School of Medicine. The first of these primary tumors to be evaluated is the oligodendroglioma. Material and Methods A review of the records of patients seen between 1930 and 1961 disclosed 37 cases of histologically proved oligodendroglioma. Slightly less than half were treated by subtotal excision and radiation therapy, the others by subtotal excision alone. Of the 37 patients, 16 were male and 21 female. Ages ranged from ten to sixty years with 30 of the patients in the third, fourth, or fifth decade. The major presenting symptoms were seizures in 19 patients, headaches in 13, muscle weakness in 2, and in 3 patients, decreasing vision, personality change, or diplopia, respectively. The duration of symptoms preceding surgery ranged from one week to eighteen years with an average of three years. The tumor was within the cerebral hemisphere in 32 patients and occupied the frontal lobe in 18. Four tumors were located chiefly within the ventricles and 1 arose from the quadrigeminal plate. Calcification was evidenced roentgeno-graphically in 24 cases and microscopically in 29. In each case an attempt was made to remove as much tumor as possible: the surgical therapy represented a positive effort at resection, and at no time was the surgeon content with a mere biopsy. On the other hand, the nature of the growth was usually recognized by its gross characteristics during the operative procedure and/or in the microscopic findings on frozen sections obtained at the time. Extirpation was never deliberately extended into the rolandic region, the basal ganglia, or areas of the dominant hemisphere when gross involvement of these areas was not apparent. The authors have no delusions regarding the surgical resect-ability of these lesions; in no instance, in their opinion, was the resection of the tumor regarded as complete. Five patients died within fourteen days following operation. Of the remaining 32, 16 received postoperative radiation therapy.