Transesophageal echocardiography (TEE) has an important role during congenital heart surgery. TEE in small infants is associated with complications, including an inability to pass the TEE probe, esophageal trauma, airway compression, aortic compression, and interference with ventilation. Recently, a monoplane intravascular ultrasound catheter (IVUC) has been developed for intracardiac echocardiography. The efficacy of IVUC for transesophageal use has been shown in numerous animal studies and several human studies, but there have been few reports involving small infants using an IVUC probe. We examined 15 pediatric patients undergoing congenital cardiac surgery using an 8-Fr AcuNav IVUC probe. We checked the cardiac anatomy, cardiac function pre-operatively and de-aeration before weaning from CPB; the surgical repairs were evaluated post-operatively. Although the IVUC probe has limitations associated with the monoplane, we found the IVUC probe to be useful in small infants and safer than the TEE.