The authors report a case of an anomalous left coronary artery discovered by chance in a totally asymptomatic 39 year old man. Appearances of anterior myocardial infarction were observed on routine preoperative ECG in a man with multiple injuries. Coronary angiography showed an anomalous left coronary artery arising from the main pulmonary artery. Left ventricular function was poor with associated mitral regurgitation. Surgical correction consisted in an end-to-end venous graft between the ostium of the coronary artery detached from the pulmonary artery and the right anterior border of the ascending aorta. Left ventricular function did not improve four months after surgical correction. The irreversibility of the myocardial lesions argues in favour of an early correction of this malformation.