The beneficial effect of transesophageal echocardiography (TEE) on medical and surgical treatment of children with congenital heart disease has been established. Its cost-effectiveness, however, has not been extensively studied. We analyzed reports of 580 routine TEE examinations performed in our institution between January 1994 and December 2003 in patients younger than 17 yr who required congenital cardiac surgery. After excluding patients who died immediately postoperatively, we identified 33 patients (5.7%) who required a second bypass run on clear-cut indication, i.e., surgical reoperation, and who clearly benefited from TEE findings. An estimate of both fixed and variable costs revealed a savings of 850 to 2655 Swiss francs (CHF) ($690 to $2130 US) per child. This figure undoubtedly underestimates the true cost-effectiveness of routine intraoperative TEE in this setting because we used mostly conservative estimates of the benefits and liberal estimates of the costs. The potential benefits of TEE in hemodynamic monitoring and medical management, in reduction of postoperative morbidity, and in improvement in the quality of life are intangible and were not considered. Although benefits and costs vary according to market conditions, patient populations, surgical practice, and technical expertise with TEE, our analysis demonstrates substantial cost-effectiveness in the use of routine TEE during pediatric cardiac surgery.