Sporadic adrenomedullary hyperplasia (AMH) is characterized by a clinical history of hypertension, increased plasma and/or urinary catecholamine levels and histomorphometric evidence of increased adrenal medullary mass in the absence of MEN 2 syndrome. The case of a 42-year-old female patient is reported who presented with typical clinical and laboratory findings of episodic hypertension and elevated plasma and urinary catecholamines. Sonography and computed tomography revealed no abnormality, but 131I-metaiodobenzylguanidine (131I-MIBG) scintigraphy showed increased uptake in the right adrenal. Transabdominal unilateral adrenalectomy was performed. The right adrenal gland was macroscopically inconspicuous. Upon histomorphometry, however, an increased adrenal medullary cell mass was shown, thus confirming AMH. Two years following surgery the patient is asymptomatic and normotensive.