Objective-To evaluate changes in cognitive and academic functioning following cardiac surgery in children with congenital heart disease. Design-A prospective cross sectional study in which patients were assessed immediately before treatment and 12 months later. Patients-Three groups of children aged 3.5-17 years: a group with congenital heart disease awaiting surgery, another awaiting bone marrow transplantation, and a healthy comparison group. Main outcome measures-Intelligence quotient and measures of academic attainment, evaluated with the British Ability Scales. Results-Preoperatively, children with cyanotic lesions showed deficits in comparison with those with acyanotic lesions. Postoperatively, children with cyanotic lesions showed a deterioration in performance and achieved significantly lower scores than those with acyanotic lesions. While there were significant diVerences between the congenital heart disease and bone marrow transplantation groups preoperatively, these were no longer apparent at follow up. Conclusions-In contrast to previously published findings, the present results suggest that cardiac surgery does not result in early postoperative improvements in cognitive function for children with congenital heart disease. The nature of the cardiac lesion continues to aVect cognitive and academic performance, even after surgery. (Heart 2001;85:687-691)