We present two- and three-dimensional transesophageal echocardiographic findings of two adult patients who presented for reoperation after previous repair of a partial atrioventricular (AV) septal defect. Both patients had a cleft in the left AV valve with severe regurgitation. One patient had an additional 10 x 5 mm defect connecting the left ventricle to the right atrium through the AV junction. Three-dimensional echocardiography was superior to two-dimensional echocardiography in comprehensively delineating the anatomical defects in the left AV valve and the AV junction.