['Mediastinitis is an infrequent, but significant complication of median sternotomy. Perioperative hyperglycemia is associated with increased morbidity, including infection in pediatric and adult cardiac surgical patients. We hypothesized that perioperative blood glucose levels would be higher in patients who later developed mediastinitis.', 'We examined the medical records of all infants and children diagnosed with poststernotomy mediastinitis (n = 24) from July 2001 to December 2005. Data recorded included postoperative blood glucose levels, age, diagnosis, operation, surgical complexity score, duration of operation and cardiopulmonary bypass, delayed sternal closure, perioperative use of steroids and total parenteral nutrition, and duration of postoperative inotropic and ventilatory support. Records of patients without mediastinitis matched for age, complexity score, and month of operation (control group, n = 32) were also reviewed. Data were analyzed with t-tests and chi-square tests. Variables with P < 0.21 on univariate tests were entered into a multivariate logistic regression model.', 'Initially, postoperative blood glucose levels were elevated, but similar in both mediastinitis and control groups. The number of subjects having peak blood glucose levels >7.2 mm (>130 mg.dl(-1)) during the first 24 h was greater in the mediastinitis group (P = 0.07). The significant multivariate predictor of mediastinitis was 24 h peak blood glucose >7.2 mM (>130 mg.dl(-1)) (P = 0.039).'] Is postoperative hyperglycemia associated with mediastinitis following pediatric cardiac surgery?