BACKGROUND Coronary artery bypass grafting (CABG) is associated with higher operative risk in the elderly compared to younger patients. The aim of this study was to evaluate risk factors for perioperative mortality after CABG in the elderly. METHODS We investigated 325 consecutive patients aged 75 or over undergoing isolated CABG at our institution. We analyzed the patients' characteristics and perioperative outcome. Patients were divided into survivors and non-survivors; risk factors and complications were compared. Based on this, we performed a multivariate logistic regression analysis to determine independent risk factors for perioperative mortality. RESULTS Non-survivors of CABG more often suffered from concomitant extracardiac atherosclerosis (non-survivors, 62.2 %; survivors, 40.6 %; p = 0.013) as well as from renal insufficiency preoperatively (non-survivors, 35.1 %; survivors 8.0 %; p < 0.0001). A trend towards higher incidences of impaired left ventricular function (non-survivors, 37.8 %; survivors, 29.9 %; p = 0.105) and a history of recent myocardial infarction (non-survivors, 29.7 %; survivors, 17.0 %; p = 0.061) were found in non-survivors compared to survivors. Furthermore, non-survivors more often underwent CABG with cardiopulmonary bypass (CPB non-survivors, 96.1 %; survivors 70.6 %; p = 0.0005). Multivariate logistic regression analysis revealed that preoperatively impaired renal function (OR: 2.857, p < 0.0001), use of CPB (OR: 5.952, p = 0.0175), extracardiac atherosclerosis (OR: 1.581, p = 0.0228), and recent myocardial infarction (OR: 1.574, p = 0.0405) were independent risk factors for perioperative mortality. Comparison of patients undergoing CABG with or without CPB reveals that patients operated without CPB had a higher preoperative risk than patients undergoing CABG with CPB. CONCLUSION These results show that besides impaired renal function, extracardiac atherosclerosis, and history of recent myocardial infarction, the use of CPB is a major risk factor for CABG in the elderly. Perioperative mortality and morbidity can be significantly reduced if CPB is avoided.