OBJECTIVE We evaluated coronary artery bypass grafting (CABG) in which aortic cross-clamping is not done due to severe atherosclerosis of the ascending aorta. METHODS Subjects were 51 patients undergoing CABG without aortic cross-clamping during cardiopulmonary bypass under moderately hypothermic ventricular fibrillation in the 12 years from June 1988 to October 1999 (Group N). In some cases, empty beating or moderate hypothermic circulatory arrest was used. We compared these 51 with 1104 subjects undergoing conventional CABG with aortic cross-clamping and cardioplegic cardiac arrest in the 9 years from June 1988 to December 1997 (Group A). RESULTS In all 6 cases with neurologic deficits, moderately hypothermic circulatory arrest was used during proximal anastomosis of saphenous vein grafts. Postoperative computed tomography scan showed them to have suffered infarction due to embolization. Multivariate analysis identified proximal saphenous vein grafting under moderately hypothermic circulatory arrest as a predictor of neurologic deficit. Complete revascularization was significantly lower in Group N. Actual survival and freedom from cardiac death were significantly lower in Group N. CONCLUSIONS Manipulation of the atherosclerotic ascending aorta under moderately hypothermic circulatory arrest or ventricular fibrillation generates the highest risk of perioperative neurologic deficit and should thus be avoided. In-situ arterial grafting should be conducted with utmost care.