In the multiple endocrine neoplasia (MEN) type II syndrome, pheochromocytomas become manifest at a later age than medullary thyroid carcinomas (MTC) do. The present report concerns a 13-year-old boy, belonging to a MEN-IIA kindred, who was admitted because of convulsive seizures related to hypertensive encephalopathy. A pheochromocytoma was suspected immediately and appropriate medical therapy was initiated. A right adrenal pheochromocytoma was removed, as well as a pheochromocytoma of an accessory right adrenal gland. Today, three years later our patient is still asymptomatic and the results of the thyroid C-cell provocative tests remain normal. This case clearly justifies the conclusion that periodic investigation of MEN-II family members to detect both medullary thyroid carcinoma and pheochromocytoma should begin early in life, as the latter may be the initial life-threatening expression of the disease. Long-term follow-up of patients treated with unilateral adrenalectomy will permit better definition of the risk of contralateral recurrence in such cases.