Two-dimensional echocardiograms and angiocardiograms were obtained in six infants and children, each with complete transposition of the great arteries, a ventricular septal defect and subvalvular pulmonary stenosis. In each case, the subpulmonary stenosis resulted from redundant tricuspid valve tissue which protruded through the ventricular septal defect and into the left ventricular outflow tract. Angio-echocardiographic correlations demonstrated features that allowed preoperative recognition of this unusual type of subpulmonary stenosis. The left ventricular angiogram in an anteroposterior orientation revealed a characteristic filling defect in the outflow tract during systole in each patient. Echocardiographic images of the left ventricular outflow tract and of the tricuspid valve demonstrated subpulmonary stenosis caused by protruding redundant tricuspid valve tissue (resembling a "pouch") in all six patients. These findings were contrasted with those from three patients with normally related great arteries and a similar, but nonobstructive, tricuspid valve pouch. Echocardiographic and angiocardiographic examination and correlation allowed preoperative diagnosis of this unusual form of subpulmonary stenosis in complete transposition of the great arteries. This is especially important because limited left ventricular intraoperative exploration may fail to reveal subpulmonary obstruction as the pouch may be flaccid in a relaxed arrested heart.