M-mode echocardiographic delineation of double-outlet right ventricle (DORV) has relied primarily on the demonstration of mitral-semilunar valve discontinuity--a feature that requires an interpretation of spatial anatomic relationships. Thirty-six patients with DORV were examined by wide-angle real-time two-dimensional echocardiography. Anatomic diagnosis was established by surgery in 28 patients and by angiography alone in eight. Typical two-dimensional echocardiographic features were (1) parallel orientation and origin of both great arteries from the anterior right ventricle, (2) mitral-semilunar valve discontinuity demonstrated on parasternal long-axis scans by the presence of muscular conus separation, and (3) absence of left ventricular outflow other than a ventricular septal defect. This technique also allows better recognition of spatial orientation of the great arteries and the position of the ventricular septal defect relative to the great arteries. An unexpected finding was a high incidence of atrioventricular valvular anomalies, particularly annular override or abnormal chordal attachments (straddling) (eight patients), isolated cleft of the mitral valve (two patients), and complete atrioventricular canal (five patients). Thus, these two-dimensional echocardiographic findings have allowed improved noninvasive recognition of DORV and the demonstration of associated anomalies that previously were unrecognized preoperatively.