Preoperative demonstration of coronary arterial anatomy may be important for babies undergoing the arterial switch operation. Echocardiography is clearly useful, but may not unequivocally show all coronary branches. Standard angiographic views can be confusing. An improved angiographic projection in which the frontal x-ray tube is caudally angled, resulting in a "laid-back" position of the image intensifier and cine camera, provides superior visualization of the coronary arteries and their relation to the aorta and the pulmonary artery. The balloon occlusion technique is used for opacification of the aortic root from the transvenous approach. Injection of 1 ml/kg of contrast delivered in 1/2 to 1 second provides the best images. The caudal aortogram is easier to interpret than standard views and facilitates description and recognition of various coronary patterns. The relation between the pulmonary artery and the aorta, the origins of the coronary arteries from the facing sinuses and their proximity to the intercoronary commissures, and the myocardial distribution of each coronary vessel are shown clearly. The caudal view therefore offers significant advantages over conventional projections for demonstration of coronary arterial anatomy in infants with transposition of the great arteries or double-outlet right ventricle.