The objective of this study was to determine the prevalence of postoperative hyperglycemia in pediatric patients following surgery for congenital cardiac defects and its impact on morbidity and mortality. It was designed as a retrospective cohort study in a pediatric intensive care unit of a university-affiliated free-standing children's hospital. A cohort of 213 patients who underwent 237 surgical procedures for repair or palliation of congenital cardiac defects comprised the study. Postoperative blood glucose measurements and all clinical and laboratory data were compiled for the first 10 days after surgery. The intensity and duration of hyperglycemia were analyzed for association with hospital morbidities and mortality. Mild and severe hyperglycemia were highly prevalent in our cohort (97% and 78%, respectively). Survivors had significantly lower peak (289.7 +/- 180.77 mg/dl vs. 386 +/- 147.95 mg/dl), mean (110.13 +/- 36.22 mg/dl vs. 146.75 +/- 57.12 mg/dl), and duration (2.59 +/- 2.3 days vs. 5.35 +/- 2.8 days) of hyperglycemia compared to nonsurvivors. Duration of hyperglycemia was independently associated with morbidity [odds ratio (OR): 1.95; p < 0.001] and mortality (OR: 1.41; p = 0.03) by multivariate logistic regression. Hyperglycemia is common in children following surgical repair or palliation of congenital cardiac defects. Postoperative hyperglycemia is associated with increased morbidity and mortality in these patients.