Reoperation for myocardial revascularization using the internal mammary artery. From October 1984 up to February 1989, 40 patients had "redo" myocardial revascularizations using one or both internal mammary arteries (IMA) in over 1000 cases operated upon in our Department for coronary bypass grafts. Thirty-one patients had a further operation for unstable angina difficult to control with drugs. Mean interval of recurrence of angina after previous surgery was 48.5 months for all the cases, but the mean interval before the second bypass operation was 68 months. Severe disease of previous vein grafts was the reason for surgery in 25 patients and progressive atherosclerosis in native coronary arteries in 15 patients. Twenty-one patients had a single mammary artery; both mammary arteries were used in 19. Two cases had endarterectomy on left anterior descending (LAD). Four patients had peroperative acute myocardial infarction (AMI), 3 a low cardiac output syndrome, postoperative bleeding occurred in 3 cases and wound infection in one case. An intraaortic balloon pump was used preoperatively in one case and coming off bypass in two others. One patient died on the second day postoperatively from cardiac arrest following bilateral pneumothorax. There were no late deaths. At a mean follow-up of 20.5 months, 28 patients are free of symptoms but 11 are complaining of angina, 5 during exercise and 6 at rest. An exercise test was positive in 8 patients. 