SummaryIn order to discuss by-pass indications for coronary syndroms, it is necessary to know perfectly well the anatomical lesions.Unfortunately, chances of success are not too good in this field, especially for the following reasons : the usual size of the stenosis, the small section of the corresponding arteries, the special risks due to the abnormal myocardium.Surgery can nevertheless be considered in certain cases, especially when medical treatment fails; the best indication being syphilitic angina pectoris.In far more common atherosclerosis, the theoretical indications for bypass would be : angina pectoris at exertion, lasting since more than six months, appearing in a young worker—a few cases of status anginosus, resisting to all coronary and extra-coronary treatments - perhaps even certain cases of incipient cardiac failure in young patients with coronary insufficiency.A good coronary arteriography should allow to select the few cases with enough localized anatomical lesions to permit good surgical compensation. One should prove by coronary arteriography that the permeability restored by surgery can usually be maintained, despite the small section of the coronary ramifications.