A case of choristoma of the posterior lobe of the pituitary is presented. The clinical presentation suggested chromophobe pituitary adenoma and the true diagnosis was only established on histological esamination. Despite the patient's advanced age her-operative course was satisfactory, but the disturbances of endocrine and visual function remained virtually unchanged. Perusal of the literature shows that this is the twentieth case of suprasellar or neurohypophyseal choristoma so far published. It provides an opportunity to review the clinical presentation, radiology and treatment, as well as to discuss the histiogenesis and nature of this rare pituitary tumor.