A 67-year-old man with a presumptive diagnosis of a pheochromocytoma presents for elective adrenalectomy the following morning. His past medical history is unre-markable, except for symptoms leading to the establish-ment of his clinical diagnosis. Approximately 6 months before admission, the patient suffered from spontaneous episodes of headaches, sweating, and frequent palpitations. Because of these symptoms, he sought the advice of his internist, who ordered a series of tests that included determination of urinary catecholamines and metabolite concentrations. Results of these tests were elevated above normal values, and a subsequent computed tomography scan of the abdomen confirmed the presence of an adrenal mass. The internist started the patient on oral phenoxy-benzamine therapy (10 mg by mouth, twice daily) in preparation for the surgical resection.