This report describes a case of epinephrine predominant pheochromocytoma successfully managed intraoperatively with an infusion of diltiazem. A 50-yr-old woman with a 10-yr history of diabetes mellitus was admitted to the hospital because of thirst and general fatigue. A cystic left adrenal tumor was found on computed tomographic scan. Although resting plasma catecholamine levels were normal, plasma norepinephrine and epinephrine levels obtained from the left adrenal vein were 1.6 ng.ml-1 (normal, 0.04-0.35) and 6.2 ng.ml-1 (normal, less than 0.12), respectively. Diltiazem was administered i. v. at a rate of 3 micrograms.kg-1.min-1 before induction of anesthesia. Anesthesia was induced with enflurane 2-3% and nitrous oxide in oxygen, followed by tracheal intubation facilitated with vecuronium. Anesthesia was maintained with enflurane 1-3% and nitrous oxide in oxygen. Paralysis was maintained with vecuronium. Hypertension during the manipulation of the tumor was controlled by increasing the inspired concentration of enflurane or by increasing the infusion rate of diltiazem to 5 micrograms.kg-1.min-1. There was no tachyarrhythmia. The infusion of diltiazem was continued until the draining vein from the tumor had been ligated. Hypotension, after removal of the tumor, was treated by the rapid infusion of fluid. Plasma norepinephrine and epinephrine levels during tumor manipulation were 1.18 ng.ml-1 and 6.57 ng.ml-1, respectively.