BACKGROUND The rapid expansion of pediatric cardiovascular surgery, along with the increase in the number of centers and operations, has also increased the use of intraoperative transesophageal echocardiography (TEE). Preoperative TEE allows for the confirmation of diagnoses established by transthoracic echocardiography and angiography, and also identifies possible additional pathologic conditions. TEE is also used to follow up on surgical repairs, determine the need for reintervention, and evaluate myocardial performance and the need for inotropic treatment. Our intention is to share the TEE findings before and after intervention for congenital heart disease in patients who received operations at our center, and the conclusions reached. METHODS From October 2009 to February 2013, 1008 patients underwent surgery for congenital heart disease. Of these, 265 were subjected to TEE in the operating room. Each patient entering the operating room with TEE planned had the echocardiography probe placed while intubated under general anesthesia. TEE studies used a GE Vivid S5. Different investigations, according to the patients' particular pathologic conditions, were also performed in addition to standard TEE studies. RESULTS Of the 265 patients for whom surgery was indicated by transthoracic echocardiography and other appropriate examinations, 260 had the diagnosis confirmed by preoperative TEE and the indicated intervention was performed. For the remaining 5 patients (1.8%), the intervention plan was changed following preoperative TEE. Cardiopulmonary bypass was reinitiated in 12 (4.5%) patients because of residual defects identified by postoperative TEE. Thus, the preoperative plan was changed in 17 (6.4%) patients out of a total of 265 owing to preoperative and postoperative TEE findings. CONCLUSIONS The use of intraoperative TEE in surgical centers for congenital heart disease allows for a significant reduction in mortality and morbidity. Intraoperative TEE performed by experienced pediatric cardiologists is therefore an absolute necessity.