Right ventricular (subaortic) obstruction has only rarely been described in complete transposition of the great arteries. Five patients with complete transposition of the great arteries in whom subaortic stenosis was angiocardiographically demonstrated were studied. All had a pressure gradient of 30 to 55 mm Hg across the aortic outflow tract. Two of the patients manifested mild tricuspid insufficiency, and another two had coarctation of the aorta. The etiologic, anatomic, hemodynamic and prognostic aspects of this unusual anomaly are discussed. An angiocardiographically demonstrated series of this anomaly has not been reported on before.