RADIATION therapy for intracranial neoplasms occasionally evokes necrosis of the brain.1,2The neurological deficits due to radiation necrosis are usually delayed, occurring several months to several years after the therapy; this may lead to an erroneous diagnosis of the recurrence of the original tumor.1-4This report concerns a case of radiation necrosis of the hypothalamus and optic chiasm following surgical and radiation therapy for a craniopharyngioma. Terminal endocrinological and neurological manifestations in this patient were clinically ascribed to recurrent craniopharyngioma. The pathological changes in the brain of this patient illustrate the significance of the vascular alterations in the production of delayed radiation necrosis. Report of a Case A 44-year-old woman was admitted to Montefiore Hospital and Medical Center in July 1965 because of progressive visual loss for several months and generalized headaches with occasional vomiting for two weeks. Her menopause occurred one year ago and since then,