The purpose of this study is to examine prospectively the efficacy of intraoperative transesophageal echocardiography (TEE) monitoring in reducing the incidence of residual ductal flow during video-assisted thoracoscopic (VATS) patent ductus arteriosus (PDA) interruption. Thirty consecutive patients undergoing PDA interruption via the VATS procedure were monitored with an appropriately sized Hewlett-Packard color-Doppler TEE probe. All examinations were performed by the same individual and interpreted with a cardiologist. Real time TEE monitoring was used, but the results were not disclosed to the surgeon until he was prepared to close the wound. The mean age was 2.4 yr and the average weight 11.2 kg. Two patients had residual flow after placement of the vascular clip. One patient had residual flow detected intraoperatively after placement of the vascular clip and residual flow was quickly abolished by the placement of a second clip, thus avoiding a reintervention. A follow-up transthoracic echocardiography was performed on 18 patients 1 mo postoperatively. Three patients presented residual ductal flow. This study using a novel application of TEE, demonstrates that TEE monitoring during PDA interruption may improve the surgical result, thus avoiding reintervention and the complications associated with residual ductal flow. However, late recurrence due to recanalization may occur and may not be detected by intraoperative TEE monitoring.