Aortic dissection is a medical emergency requiring prompt diagnosis and maybe emergency surgery especially if the ascending aorta is involved. We have performed transesophageal echocardiography(TEE) in 22 consecutive patients with suspected aortic dissection. The diagnosis was subsequently proven in 14 patients(9 males, 2 females, mean age 51+/-11years) on the basis of TEE. The results and effectiveness were compared with computed tomography (CT) and aortography. Seven patients had type I aortic dissection, three had type II and four had type III. Twelve patients had hypertension. There was aortic regurgitation in five of seven patients with type I dissection and in all three patients with type II dissection. Type I dissection was found by TEE in seven patients who had intimal flap showing parallel movement to the aortic wall. CT was positive in only three of five of these patients. Type II dissection was seen in three patients by TEE. CT demonstrated dissection in one of three of these patients. In one patient the false lumen was filled with a thrombus, which was negative at angiography. Type III dissection was found by TEE in four patients. CT was positive in two of four patients. Aortography was performed and positive in one patient. The starting point of aortic dissection could be demonstrated in all four patients by TEE. TEE was well tolerated by patients with aortic dissection and associated with no major complications. In conclusion. TEE was very useful in detecting aortic dissection and in providing a dynamic information of the intimal flap and of the presence and extent of luminal thrombus with flow dynamics.