Elevated blood glucose following coronary artery bypass graft (CABG) is associated with an increased risk of surgical wound infection (SWI). It is unclear whether hyperglycaemia, the diabetic state, the longstanding vascular effects of diabetes, or the systematic inflammatory response confers the increased vulnerability to SWI. This study was designed to examine the significance of postoperative blood glucose control as a risk factor for SWI after vein graft harvesting on the leg and sternotomy. Patients with and without diabetes had a CABG within 60 days to be eligible. The present study was part of a larger protocol investigating SWI following CABG in a total of 374 patients. Potential risk factors, duration of diabetes, pre-operative glycated haemoglobin (HbA(1c)) and presence of long-term complications were recorded. All patient records were reviewed retrospectively to record 10% glucose infusions during the operation, and blood glucose concentrations and insulin therapy on postoperative days 0, 1 and 2. Patients were contacted by telephone 30 and 60 days after surgery and interviewed in accordance with a questionnaire about symptoms and signs of wound infection. In the present study, it was not possible to separate the effect of diabetes as a risk factor for SWI from that of hyperglycaemia. However, in the subgroup of patients without a pre-operative diagnosis of diabetes, increased blood glucose concentrations during postoperative days 0, 1 and 2 was associated with an increased risk of mediastinitis.