Pheochromocytoma is an unusual cause of hypertension during pregnancy. We present a 40-year-old woman who had a myocardial infarction during pregnancy in whom pheochromocytoma was subsequently diagnosed. This disorder carries a high risk of maternal and perinatal mortality, if undiagnosed prior to delivery. Therefore, the diagnosis of pheochromocytoma should be considered in pregnant patients who exhibit a marked fluctuation in hypertension. Urinary concentrations of catecholamines and their metabolites should be measured in such cases.