Objective: The purpose of this study is to investigate the elevated blood glucose levels in the postoperative period are associated with an increased risk of deep wound infection in diabetic individuals undergoing lumbar spine surgery. Methods: Of 2896 patients who underwent lumbar spine operations by one surgeon between 1993 and 2002, 329(11.4%) were diabetics. The rate of deep wound infections in diabetic patients was 6.4%, versus 3.2% for nondiabetics. 152 patients had their operation before implementation of the protocol and 177 after implementation. Charts of the diabetic patients were reviewed. Mean blood glucose levels were calculated from documented results of finger-stick glucometer testing. Results: Twenty-one diabetic patients suffered deep wound infection. Infected diabetic patients had a higher mean blood glucose level through the first 2 postoperative days than noninfected patients($230{pm}6.9$ versus $175{pm}3.8mg/dL$; p<0.003) and had a long operation time($216{pm}57.9$ versus $167.5{pm}42.2$ minute; p<0.05). Multivariable logistic regression showed that mean blood glucose level for the first 2 postoperative days, long operation time, and use of the instrumentation(p<0.02) were all related predictiors of deep wound infection. Institution of a protocol of postoperative continuous intravenous insulin to maintain blood glucose level less than 200mg/dL was began in september 1997. This protocol resulted in a decrease in blood glucose levels for the first 2 postoperative days and a concomitant decrease in the proportion of patients with deep wound infection, from 8.3%(11/132) to 5.1%(10/195) (p<0.02). Conclusion: The incidence of deep wound infection in diabetic patients is reduced after implementation of a protocol to maintain mean blood glucose level less than 200mg/dL in the immediate postoperative period.