Diabetes mellitus (DM) and hyperglycemia are associated with increased surgical morbidity and mortality. Hyperglycemia is a determinant of risk of surgical complications and should be addressed across the continuum of surgical care. While data support the need to address hyperglycemia in patients with DM in the ambulatory setting prior to surgery and in the inpatient setting, data are less certain about hyperglycemia occurring during the perioperative period-that part of the process occurring on the day of surgery itself. The definition of "perioperative" varies in the literature. This paper proposes a standardized definition for the perioperative period as spanning the time of patient admission to the preoperative area through discharge from the recovery area. Available information about the impact of perioperative hyperglycemia on surgical outcomes within the framework of that definition is summarized, and the authors' approach to standardizing perioperative care for patients with DM is outlined, including the special case of patients receiving insulin pump therapy. The discussion is limited to adult ambulatory non-obstetric patients undergoing elective surgical procedures under general anesthesia.