An aortico-left ventricular tunnel was diagnosed at echocardiography in a 6 week old baby after fortuitous detection of a systolic and diastolic murmur. Its association with atresia of the right coronary ostium, suspected at echocardiogoraphy, was confirmed at surgery which included occlusion of the tunnel orifices, aortic commissurotomy and reimplantation of the right coronary artery. The short-term postoperative result is excellent. This is an exceptional malformation, the clinical diagnosis of which is relatively easy. Its relationship with the right coronary artery conforms to an embryological logic and must be investigated thoroughly before surgery to avoid compromising myocardial revascularisation.