Coronary bypass surgery is now a well-established treatment for coronary artery disease. There is still controversy as to when surgery should be recommended. Taking into account a patient's age, coronary anatomy, degree of ischemia and left ventricular function, one can use available data to define the expectations for bypass surgery with reasonable accuracy. If important ischemia is present and the coronary anatomy is favorable, bypass surgery should improve the patient's quality of life and may significantly enhance survival.