Patients with diabetes mellitus are subjected to major operations more frequently than those without diabetes. Although many of these operations are done on an elective basis, the perioperative control of blood glucose levels--ranging from 6.7 to 13.3 mmol per liter (120 to 240 mg per dl)--remains a therapeutic challenge. In planning the management, the type of diabetes, current treatment, the degree of recent control, the presence of complications, and the type of surgical procedure must all be considered. All insulin-dependent patients and many non-insulin-dependent ones need insulin therapy perioperatively. The variable stress associated with major procedures such as coronary artery bypass and kidney transplantation makes a flexible insulin regimen desirable, which can be provided using a continuous insulin (regular) infusion system and frequent bedside blood glucose monitoring. Implementing such a regimen facilitates rapid control before an operation and a quick response to blood glucose changes during the procedure and provides a convenient and predictable method of control during the postoperative period.