We examined the echocardiograms of 40 patients with double oudet right ventricle, proven either at autopsy or during surgery. By way of the subcostal approach, it proved possible to determine the insertion of the outlet (infundibular) septum and to categorize the malformations within the classification proposed by de la Cruz and her colleagues. It was also possible to ascertain the relationships of the atrioventricular valves with one or with both infundibulums, and these features could be correlated with infundibular interrelationships. The interrelationship of the great arteries, in contrast, was not always in accordance with the infundibular interrelationships, indicating that the arterial interrelationship may not prove to be a good parameter for surgical decision-making. Of greatest importance was the visualization and echocardiographic appraisal of the spatial position and size of the ventriculoinfundibular fold, since this anatomic feature was the key to determining the optimal surgical approach. This is so because the ventriculoinfundibular fold constitutes one of the borders of the ventricular septal defect, and separates it from the plane of the leaflets of the arterial valves. Furthermore, the fold frequendy contributes to infundibular obstruction. Our echocardiographic studies, based on a better anatomic knowledge, permitted us to choose the most suitable surgical technique in our patients.