A rare case of anomalous origin of the right coronary artery from the pulmonary artery associated with a large aortopulmonary window in a 4-month-old boy is reported. The right coronary artery is exposed to systemic pressure and carries fairly well-oxygenated blood to the myocardium. Angiographic diagnosis could be difficult because of the simultaneous filling of both great arteries which obscures the origin of the anomalous vessel. Closure of the aortopulmonary window alone could result in acute myocardial ischaemia. A plastic procedure for correction of this association of defects, which should allow normal growth, is described.