The outcome of coronary artery bypass surgery is best assessed in terms of two independent components: the operative mortality and complications on the one hand, and the late survival and relief of symptoms on the other. The expected operative mortality rate in a particular patient can be calculated with reasonable accuracy from preoperative risk factors. This calculation also enables results from different units to be compared by correcting for the preoperative risk factors in the patient population. Despite improvements in cardiopulmonary bypass, there is still a low but appreciable incidence of subtle neuropsychological changes induced by coronary artery bypass grafting. The expected long-term results of the procedure must be determined from the results of surgery in the past. However, allowance must be made for two new influences. One is the expected improvement in the long-term results of current surgery, due to the improved longevity of currently used graft conduits such as the internal mammary artery. The other is the worsening of late results of present-day coronary artery bypass grafting caused by the greater number of preoperative risk factors in patients currently accepted for surgery, such as old age, impaired left ventricular function, and reoperation.