Coronary artery to coronary sinus fistula is a rare congenital disorder. Aortography and selective coronary angiography are currently the diagnostic modes of choice for the evaluation of congenital coronary artery fistulas, but recent reports have demonstrated the usefulness of noninvasive techniques.1-3 We describe 3 patients in whom the relatively new technique of transesophageal echocardiography was found useful not only in the diagnosis and precise localization of these lesions but also in the intraoperative evaluation of the surgical repair (Table I, Figures 1 to 3). All transthoracic 2-dimensional and color Doppler examinations were done in the standard manner using a commercially available system and a 2.0 or 2.5 MHz transducer.4 Intraoperative transesophageal echocardiographic studies were also performed in the standard manner5 using a 5 MHz transducer (Hewlett-Packard 77760A system for patients 1 and 2 and Aloka 870 biplane system for patient 3). The proximal coronary arteries were examined using the standard basal shortaxis view6 and the coronary sinus outlined in the right ventricular inflow plane. © 1991.