Hyperinsullinism and the resultant hypoglycemia are hallmarks of functioning beta islet cell tumors of the pancreas. The management of one case of insulinoma during surgery for the removal of the tumor is described and the available literature on the subject reviewed. The outline of the anesthetic management for the insulinoma is as follows: 1) Anesthetists should understand the signs and the symptoms of hypoglycemia and hyperglycemia. 2) Preoprative management: a) infusion of glucose for avoiding hypoglycemia due to NPO after midnight. b) glucocorticosteroid administration with premedications. 3) Operative management: a) continuous determination of blood glucose level may be helpful. b) Maintenance of the glucose level about 50mg% above symptomatic CNS level have the advantage that exicision of the infulinoma can be immediately judged. c) The use of an agent that decreases CMRO2 and does not affect the insulin-glucose ratio is rational choice when concern about hypoglycemia exists. Thiopental-enflurane anesthesia with controlled ventilation maintaining normocarbia is recommended. d) beta-adrenergic blocker. These drugs must be avoided in the hypoglycemic state.