Coronary artery surgery entirely relieves or very much reduces angina in over 90 per cent of patients and it can now be undertaken with a very low operative risk. Furthermore, it increases life expectancy for many angina sufferers. It has been shown to increase the probability of surviving for 5 years in those who have life-threatening forms of coronary artery disease and as figures have become available for 10-year results they confirm that this improvement in prognosis is sustained in the second 5 years after surgery. The data now available indicate that the prognosis is improved by surgical treatment in all except those with only one vessel involved or with the less hazardous forms of two-vessel disease who have a good outlook however they are managed. At present it is thought appropriate to offer surgery to all those with angina that is severe enough to limit a reasonable life style and that adequate medical treatment has failed to control. At a relatively early stage in the assessment it is desirable to know the result of a formally conducted exercise ECG test and this together with the outcome of a trial of medical management decides whether or not coronary angiography should be performed. With this further information available it is possible to take into account the improvement in prognosis with surgical treatment in patients with the more dangerous forms of coronary artery disease. Depending on the severity of the angiographic appearance, perseverance with medical measures may be appropriate.(ABSTRACT TRUNCATED AT 250 WORDS)