Pheochromocytomas are functionally active, catecholamine-secreting tumours of chromaffin tissue. The mainstay of pharmacological therapy is preoperative treatment with oral phenoxybenzamine. This drug irreversibly alkylates alpha-1-adrenergic receptors on vascular smooth muscle and renders them nonfunctional, thereby causing vasodilatation. The duration of action of a single dose is approximately 24 h. Therefore, postoperative hypotension is a hazard of therapy with phenoxybenzamine if adequate plasma volume repletion is not provided. Prazosin, a short-acting, competitive alpha-1 blocker, has been used preoperatively, but has been criticized for its failure to adequately prevent perioperative hypertensive episodes. We report the case of a 73-year-old woman who was admitted for elective pheochromocytoma resection. Preoperative therapy with phenoxybenzamine was impossible because of the patient's refusal to take the drug. Preoperative antihypertensive preparation was therefore performed with prazosin 30 mg/24 h and metoprolol 100 mg/24 h. During the surgical preparation of the tumor, sodium nitroprusside was started at an average infusion rate of 4.1 micrograms/kg/min. After resection of the primary tumor, when the sodium nitroprusside infusion was stopped the patient exhibited an increase in systolic blood pressure (BP) up to 210 mg Hg. This hypertensive crisis was managed with sodium nitroprusside, nitroglycerin, and esmolol. A multilocular pheochromocytoma was diagnosed. Further stimuli due to tumour palpation resulted in repeated increases in BP. In this manner, two additional areas of tumour could be diagnosed by BP peaks after reduction of the sodium nitroprusside infusion. After complete resection of a total of three tumours, no further hypertensive crises occurred. The patient's postoperative course was uneventful. We conclude that in this patient presenting with an unsuspected multilocular pheochromocytoma, the lack of permanent alpha-blockade was probably helpful in allowing complete resection of all the tumours.