OBJECTIVES: To determine the relative value of transesophageal echocardiography (TEE) and transthoracic echocardiography (TTE) in exploring the potential embolic source (PES) in heart and aortic arch and to study the clinical significance of aortic arch atherosclerosis (AAA). METHODS: Forty-nine patients with cerebral embolism were included in this study. TEE and TTE were used to evaluate the potential source of emboli in aortic arch, heart and duplex in the carotid artery. An atherosclerotic lesion of the aortic arch was defined as normal, mild plaque, moderate plaque, and protruding plaque or mobile plaque. RESULTS: Of the 49 patients, 31 (63%) patients showed evidence of AAA: 7 (14.1%) patients were mild, 9 (18.4%) were moderate and 15 (30.6%) were severe. In those 15 patients, 11 had neither severe ICAA nor heart disease. Thirty-three patients had internal carotid arterial atherosclerosis (ICAA). The potential sources of embolization of heart and aortic arch is 48.98% by TEE, but only 18.4% by TTE; 9 patients had heart disease. Age and ICAA were significantly correlated with AAA. CONCLUSION: At present, TEE is a better method for exploring atherosclerotic lesions in the thoracic aorta. AAA is an important potential source of cerebral embolic stroke.