Post-mortem analysis with castangiography was performed on 54 patients who died within 30 days of coronary artery bypass surgery. Myocardial failure was the cause of 85% of the deaths. There were 215 coronary anastomoses (4.0 +/- 1.1/patient), 24% of which were non-functioning. Most of the occlusions were due to various technical failures. The most striking features were 1) high occlusion rate (25%) in sequential vein grafts and 2) disastrous complications of coronary endarterectomies. Compared with preoperative angiographic data, only 15 (28%) of the 54 patients were found to have 'complete' revascularization, with patent grafts and all stenosed coronary arteries bypassed. The need for recognition and avoidance of technical complications is stressed: Failures of surgical technique constitute a major risk factor in coronary artery surgery.