Background. Perioperative myocardial injury is a major determinant of postoperative cardiac dysfunction for congenital heart disease, but its assessment during this period is difficult. The objective of this study was to determine the suitability of using postoperative serum concentrations of cardiac troponin I (cTnI) for this purpose. Methods. Cardiac troponin I levels were measured serially in the serum of patients undergoing uncomplicated repairs of atrial septal defect (n = 23), ventricular septal defect (n = 16) or tetralogy of Fallot (n = 16). The concentrations were correlated with intraoperative parameters (cardiopulmonary bypass time, aortic cross-clamp time, and cardiac bypass temperature), and postoperative parameters (magnitude of inotropic support, duration of intubation, and postoperative intensive care and hospital stay). Results. Postoperative absolute cTnI levels were lesion specific, with a pattern of increase and decrease similar for each lesion. For the total cohort, significant correlations between postoperative cTnI levels at all times (r = 0.43 to 0.83, p < 0.05) until 72 hours were noted for all parameters, except for cardiac bypass temperature. When evaluated as individual procedure groups, no significant relationships were noted in the atrial septal defect group, whereas postoperative cTnI levels were more strongly correlated with all intraoperative and postoperative parameters in the ventricular septal defect group than in the tetralogy of Fallot group. Conclusions. This study suggests that cTnI values immediately after operation reflect the extent of myocardial damage from both incisional injury and intraoperative factors. Cardiac tropinin I levels in the first hours after operation for congenital heart disease are a potentially useful prognostic indicator for difficulty of recovery.