Background. Atherosclerosis of the thoracic aorta is an independent risk factor for stroke after cardiac surgery. No attention had so far been paid to its topography. The relationship between the topography of aortic atherosclerosis and stroke was studied in patients admitted for coronary surgery. Methods. The extent and location of atherosclerosis in the ascending aorta and arch was assessed intraoperatively with epiaortic ultrasound and transesophageal echocardiography in 611 consecutive patients. They were followed for 5.5 +/- 1.7 years ( mean +/- SE), amounting to 3,358 patient-years. Results. The incidence of early postoperative (< 30-day) stroke was 6.4% in patients with atherosclerosis of the ascending aorta and 1.5% in those without ( p = 0.004). The five-year stroke-free survival rates (> 30 days after the operation) for patients without aortic disease, with less than 50%, and with greater than 50% of the ascending aorta affected, were 95.3 +/- 0.9%, 91.8 +/- 2.1%, and 65.0 +/- 14.6%, respectively ( p < 0.0001). Conclusions. Atherosclerosis of the ascending aorta stands out as a predictor of late stroke. High risk is predominantly linked to atheromas in its distal part and lesser curvature.