Symptoms and electrocardiographic changes of acute myocardial ischemia in a 10-year-old boy resulted from congenital atresia of the ostium of the left coronary artery. At 14 years of age persistence of symptoms and a positive exercise test prompted surgical treatment by aortocoronary artery saphenous vein bypass graft. Two months postoperatively, the symptoms and the abnormal findings on exercise test had subsided and forward flow through the graft to the left coronary artery was demonstrated by contrast angiography.