Fifty-four patients with oligodendroglioma presented in the past 15 years. In contrast to some widely taught concepts, oligodendrogliomas occured largely in the frontotemporal area of both cerebral hemispheres with two peaks of age incidence: one small peak in childhood, and the highest incidence in the middle-aged adult. Seizures, either major and/or minor, were the most common clinical manifestations (average 87%). Cerebral angiography and pneumography were the most reliable and useful diagnostic procedures, as well as the promising CAT scan. All 24 patients who underwent combined modalities of treatment with radical surgery and postoperative radiation therapy survived at least five years, and 2 out of 11 patients treated by surgery alone failed to survive the five-year follow-up period in addition to two recurrences. Postoperative radiation treatment is considered quite effective and indicated in most cases because complete removal of the tumor is not always possible.