Postoperative infection is not only a major source of morbidity and mortality in patients undergoing surgery, but also an important cause of increased hospital stay and resource utilization. Diabetes has been shown in multiple studies to increase the risk of post-surgical infection. More recently, hyperglycemia has been investigated as an independent risk factor for postoperative infection. This paper will review the effects of intra-operative, postoperative, and long-term glycemic control on postoperative infection rates. The mechanisms by which surgery causes hyperglycemia will be reviewed, as well as the immunologic and humeral effects of hyperglycemia.