Out of 400 consecutive patients who underwent aorto-iliac surgery 45 (11.25 per cent) were known to have coronary disease at the time of the operation. Pre-operative coronary arteriography was carried out in the 11 patients (2.75 per cent) who had unstable or recently worsened angina. Aorto-coronary bypass was performed preventively in 7 patients (1.75 per cent of surgical patients). Mortality from preventive aorto-coronary bypass and secondary aorto-iliac surgery was nil. A study of post-operative mortality (2.75 per cent overall) showed that only one patient (0.25 per cent of surgical patients) died of myocardial infarction. The low rate of post-operative morbidity and mortality of coronary origin therefore does not incline to extend the indications for preventive aorto-coronary bypass. However, it seems desirable to improve the indications for pre-operative coronary arteriography by performing thallium 201 myocardial scintigraphy with dipyridamole infusion in all coronary patients about to undergo aorto-iliac surgery when no exercise electrocardiogram can be obtained because of intermittent claudication. This type of examination will probably broaden the indications for pre-operative coronary arteriography and preventive aorto-coronary bypass, though presumably to a very small extent. Among these 400 patients who underwent aorto-iliac surgery and were all followed up for 2 to 12 years, only a few (0.25 per cent) benefited secondarily from coronary surgery, no doubt because the physiological age of that population was often too high. In fact, these patients were mainly at risk of cancer aggravated by both alcohol and smoking, for in this study, and rather in contrast with most publications, cancer was responsible for 44 per cent of secondary deaths, i.e. more than twice the percentage (20 per cent) of secondary deaths of cardiac origin.