Protruding aortic arch atheromas are associated with otherwise unexplained strokes and transient ischemic attacks. Therefore aortic atheromas also may be important in patients with carotid artery disease. Forty-five patients with > or = 50% carotid stenosis and stroke or transient ischemic attack within 6 weeks underwent transesophageal echocardiographic examination (TEE). They were matched for age, sex, and hypertension with 45 control subjects who had also had a recent cerebral event but in whom significant carotid stenosis was absent. Protruding aortic arch atheromas were present in 17 (38%) of 45 patients with carotid disease and only 7 (16%) of 45 of control subjects (p = 0.02). Mobile atheromas (with the greatest embolic potential) were present almost exclusively in case patients, 6 (13%) of 45, versus 1 (2%) of 45 control subjects (p = 0.05). Case patients with mobile atheromas had the most severe carotid stenosis ( > or = 80%). Cerebral symptoms were discordant with the side of the carotid stenosis in 10 case patients, and 4 had atheromas. In conclusion, protruding atheromas of the aortic arch are present in significant numbers of symptomatic patients with carotid artery disease. These atheromas may represent an additional cause of symptoms in patients with carotid stenosis. TEE to look for protruding aortic atheromas may be considered in patients with neurologic events despite the presence of significant carotid stenosis, especially if the symptoms are discordant with the side of carotid stenosis.