Background. Intraoperative transesophageal echocardiography and follow-up transthoracic echocardiography have been useful in assessing cardiac function in complete atrioventricular septal defects. However, it has been suggested that a discrepancy exists between intraoperative and postoperative findings, and that intraoperative findings cannot reliably predict long-term results. This study aims to determine whether this discrepancy exists and to assess whether it is possible to predict follow-up results using intraoperative transesophageal echocardiography. Methods. A retrospective analysis was made in 35 patients who underwent biventricular repair by one surgeon between November 1997 and January 2004. All patients received intraoperative transesophageal echocardiography and follow-up transthoracic echocardiography at 19.1 ± 18.02 months (range, 7 days to 5 years; median, 15.1 months). Results. In left-sided atrioventricular valve regurgitation, 34.3% (12 of 35) of patients showed discrepancy during follow-up, and 28.6% (10 of 35) showed progression of regurgitation (from grade I to II). In right-sided atrioventricular valve, 11.4% (4 of 35) of patients showed discrepancy, 9.6% (3 of 35) showed progression of regurgitation (from grade I to II). Conclusions. In complete atrioventricular septal defects, intraoperative transesophageal echocardiography did not show the same findings as that of follow-up transthoracic echocardiography in some cases. However, this discrepancy is not so great as to require reoperation in early to midterm follow-up. Therefore, intraoperative transesophageal echocardiography may be used as tool to predict durability of surgical results and to decrease the incidence of reoperation in complete atrioventricular septal defects.