Echocardiography has been used during interventional cardiac catheterization for guidance of the procedure and assessment of results. However, limited echocardiographic windows and logistical difficulties make conventional echocardiography during interventional catheterization impractical and of limited value. Transesophageal echocardiography (TEE) with Doppler color flow mapping is more useful than conventional echocardiography for guidance of interventional catheterizations. Device closure of congenital atrial and ventricular septal defects (ASDs and VSDs) and of postoperative residual interatrial and interventricular communications, balloon valvuloplasty, and Brockenbrough atrial septal puncture with ASD creation have been performed under combined fluoroscopic and TEE guidance. Transesophageal echocardiography can be performed continuously throughout the procedure, allowing simultaneous fluoroscopic and echocardiographic assessment of catheter position. Localization of individual device arms during transcatheter device closure of ASDs and VSDs is easier and more accurate when TEE is used, resulting in a lower incidence of incorrect device positioning. Doppler color flow mapping is used to determine number, location, and size of defects, to detect residual shunts after device closure, and to assess valve insufficiency after balloon valvuloplasty and other procedures. Combined TEE and fluoroscopic guidance of interventional procedures, with echocardiographic assessment of results, reduces the amount of radiation and contrast used during the procedure, allowing performance of additional interventional procedures during the same catheterization. Transesophageal echocardiography is indicated during interventional procedures in which simultaneous Doppler color flow mapping and precise localization of catheter, balloon and/or device position will result in a higher success rate and decreased morbidity.