We report a case of severe hypercalcemia and a pheochromocytoma of the right adrenal gland. The patient underwent adrenalectomy, following which the hypercalcemia disappeared. Parathormone assay of the adrenal tumor revealed high levels of activity despite normal serum parathormone activity. This suggests that the etiology of hypercalcemia in patients with pheochromocytoma is related to ectopic secretion of a parathormone ectopic peptide-like substance.