The cross-sectional echocardiographic demonstration of the "goose-neck" deformity is described in four patients with endocardial cushion defect. The diagnosis was confirmed in each patient by left ventricular angiocardiogram. The subxiphoid approach of cross-sectional echocardiography in diastole allowed visualization of an elongated, narrowed, and somewhat horizontally inclined configuration of the left ventricular outflow tract, which appeared almost identical to that obtained by angiocardiography. In systole, the right border of the left ventricle was composed of the cleft anterior mitral leaflet, the left-sided line of which was convex toward the left ventricular cavity. The mitral valvular echoes were thickened, jagged and irregular, which seemed to correspond to the scalloped appearance of the right border of the left ventricular silhouette in a systolic phase of the left ventricular angiocardiogram. There were no obvious differences between the goose-neck configuration of complete-type endocardial cushion defect and that of ostium primum atrial septal defect.