Owing to the development of transluminal angioplasty, coronary bypass surgery has now well-defined indications in patients who underwent thrombolysis. It may need to be performed in an emergency, but fortunately this only occurs in a few cases: in case of occlusion of the left main coronary vessel or equivalent lesions, when thrombolysis has failed and in case of failure of angioplasty with obliteration of large vessel and a still viable myocardium, and when the patient continues to suffer or shows signs of heart failure. The operative risk and the risk of haemorrhage then reach 10 p. 100. The installation, prior to surgery, of an intra-aortic counterpulsation system is useful in case of shock or left ventricular failure. Delayed coronary bypass is indicated mainly in case of three-vessel lesions with a less than 40 p. 100 ejection fraction, in case of stenosis of the left main coronary vessel or equivalent lesions, and in patients whose lesions are not amenable to angioplasty on a good caliber vessel, with a still viable myocardium. The operative risk in such cases is distinctly lower (2.4 p. 100). The long-term results obtained confirm the value of coronary bypass surgery when it becomes necessary after thrombolysis.