A 43 yr-old female African elephant (Loxodonta africana) collapsed acutely and died. Necropsy revealed an enlarged right adrenal medulla. Histologic appearance was typical of pheochromocytoma. Special stains and electron microscopy demonstrated chromaffin granules, suggesting that the tumor was derived from catecholamine secreting cells of the adrenal medulla, and may have been functionally secretory. Serum levels of both norepinephrine and epinephrine were elevated at time of death, supporting the functional nature of the tumor. Histologic findings of arteriolar sclerosis and smooth muscle hyperplasia suggested that the animal may have suffered from chronic systemic hypertension. Pheochromocytoma should be considered as a differential diagnosis in cases of suspected hypertension and acute death in elephants.