The major risk factors for diabetics undergoing surgery are the end-organ diseases associated with diabetes. Autonomic neuropathy is relatively common in diabetic patients and associated with an increased risk of perioperative cardiovascular instability. We experienced a case of severe bradycardia and hypotension during general anesthesia for subtotal gastrectomy in a 59 year-old male diabetic patient. Anesthesia was induced with thiopental and vecuronium, and was maintained with nitrous oxide, oxygen and enflurane. Five minutes after induction, severe bradycardia and hypotension developed without specific events. The bradycardia was unresponsive to intravenous atropine and ephedrine, but the blood pressure was restored by administration of ephedrine. During operation his blood pressure was maintained in normal range but the bradycardia was not restored by additional administration of atropine. Postoperatively, myocardial infarcton was ruled out. The test performed after operation suggested that his cardiovascular autonomic nervous system was severely impaired. We think that cardiovascular autonomic dysfunction should be evaluated during preoperative period to plan the anesthetic management and to prevent severe cardiovascular complications in diabetic patients.