Objectives: The importance of intraoperative transesophageal echocardiography in congenital heart surgery, its diagnostic accuracy and its predictive value on long-term follow-up. Study Design: This is a retrospective study done on 1156 patients in which the preoperative and postoperative transthoracic echo reports were analyzed together with the intraoperative transesophageal echo reports performed for patients undergoing ventricular and atrial septal defect closure, mitral valve repairs and right ventricular outflow tract repairs. Results: Intraoperative transesophageal echocardiography detected the highest incidence of residual pathololgy in mitral valve repairs and the least in atrial septal defect repairs. It was also helpful in defining patients in need for surgical revision intraoperatively. Intraoperative transesophageal echocardiography was most accurate in diagnosing residual mitral regurgitation and least accurate in atrial sepal defects. On follow up, residual septal defects had a tendency to close spontaneousely, residual right ventricular outflow tract gradients tended to decline, while the residual mitral valve regurgitations were liable to progress. Conclusion: Intraoperative transesophageal echocardiography has an influential role in congenital heart surgery; it may miss a significant percentage of residual defects but is able to predict the fate of residual lesions detected intraoperatively.