In a consecutive series of 4,697 patients undergoing coronary artery bypass surgery, these risk factors were found to be significant for increased postoperative mortality: age greater than 70, female sex, unstable angina, prior myocardial infarction, hypertension, diabetes mellitus, and ejection fraction less than .40. A comparison by year (1980-1988) revealed a steadily increasing incidence of these risk factors. Future analysis of coronary artery bypass mortality should include risk-factor stratification.