Authors describe one case of Cushing's disease in a old eight-year boy, with growth deficiency, pubic hair and obesity. He had hypercortisolism unresponsive to dexamethasone suppression (1 mg). The more interesting fact for localization of the lesion was the more than 50% suppression with 8 mg of dexamethasone, while tomographic studies of sella turcicaland CAT were normal. A 3 mm microadenoma was removed at transsphenoidal surgery. After surgery the patient had diabetes insipida and adrenal insufficiency. One year later all endocrinologic studies were normal. This fact underlines the importance that transsphenoidal surgery can have in the treatment of Cushing's disease.