A case of radionecrosis of the brain in a patient previously treated for squamous cell carcinoma of the scalp is presented. Cerebral angiography revealed a mass effect primarily in the right frontal area. Computed tomography showed extensive hemispheric edema. A frontal lobectomy was performed, and the recovery was excellent. The lower limit for brain tolerance for irradiation is about 5000 rads given in five weeks. This dose should not be exceeded when extracranial lesions are treated. Although computed tomography cannot diagnose brain necrosis, specifically, it should, along with the clinical history, be very helpful.