A retrospective analysis was undertaken of 365 consecutive patients, 75 women and 290 men with a mean age of 59.9 +/- 9.7 years, who had coronary artery bypass surgery during 1981. Complications classified as major were: mediastinal hemorrhage, pericardial tamponade, wound dehiscence, sternal osteomyelitis, myocardial infarction, bacterial endocarditis, dissecting aneurysm and diabetes insipidus. Complications classified as minor were: atrial fibrillation, postpericardiotomy syndrome, cellulitis, thrombophlebitis and phrenic nerve palsy. There were 48 patients (13%) with 52 major complications. Age more than 60 years, cardiopulmonary bypass time longer than 150 minutes, aortic cross-clamp time longer than 100 minutes, number of grafts greater than five and presence of diabetes mellitus were significantly associated with major complications. Complications tended to occur more frequently in women, obese patients and those with emergency operation or ejection fraction less than 30%, but the associations were not statistically significant. Physicians referring patients for coronary artery surgery should be cognizant of the incidence of morbidity along with the other risks and benefits when considering coronary artery bypass surgery.