In a previous report10 of three cases of pheochromocytoma the difficulties associated with the diagnosis were emphasized. The first was the case of a young white male with unexplained massive gastrointestinal hemorrhage. Despite intensive diagnostic laboratory and x-ray studies and two exploratory operations, the diagnosis was not made for almost three years, and the patient died of gastrointestinal and cerebral hemorrhages before the necessary surgery could be accomplished. The second and third patients were more fortunate—the awareness of their family physicians of the possibility of pheochromocytoma in any case of hypertension led to employment of proper diagnostic tests with a definite diagnosis, enabling successful treatment. The true incidence of the disease is unknown. Graham6 found pheochromocytoma in 8 (0.47%) of 1,700 patients with intractable hypertension severe enough to warrant splanchnicectomy. On that basis it is calculated to account for approximately 700 to 800 deaths annually in the United