Atherosclerotic disease of the aortic arch is thought to be a potential source of cerebral emboli, but this disease in the branch of the aortic arch has not been extensively explored. This study assessed atherosclerotic lesions in the thoracic aorta and the branches of the aortic arch using transesophageal echocardiography in patients with cerebral infarction, and simultaneously searched for potential cardiac sources for emboli. Thrombi were detected in the left atrial appendage in nine of 54 patients with cerebral infarction and these patients were excluded. The remaining 45 patients with cerebral infarction (31 males and 14 females aged 68.5 +/- 7.4 years) and 35 normal subjects (21 males and 14 females aged 69.2 +/- 9.5 years) were evaluated. The thickness of the wall was measured in the branches of the aortic arch (brachiocephalic trunk, left common carotid artery and left subclavian artery) as well as the thoracic aorta (ascending aorta, aortic arch and descending aorta). Atherosclerotic lesions were defined as increased echogenicity of the intima (intimal thickening), calcification, protruded plaque, ulceration or plaque with cystic lesion. The thicknesses of the wall in the aortic arch (3.84 +/- 1.25 vs 2.71 +/- 1.33 mm, p < 0.01), left common carotid artery (2.67 +/- 1.10 vs 2.16 +/- 0.91 mm, p < 0.05) and the left subclavian artery (2.52 +/- 0.67 vs 2.15 +/- 0.88 mm, p < 0.05) were significantly greater in patients than in the normal subjects. The incidence of plaque or ulceration was significantly increased in patients with cerebral infarction compared with the normal subjects in the aortic arch (76% vs 43%, p < 0.05) and left common carotid artery (44% vs 17%, p < 0.05). Transesophageal echocardiography can detect possible sources of emboli in the branches of the aortic arch as well as the thoracic arch in patients with cerebral infarction.