Transthoracic (tth) and transesophageal (TEE) 2D-echocardiography (E) were performed in 20 consecutively examined patients (17 males, 3 females, age 18 to 76 years, mean age 48.6 +/- 18.9 years) with dissecting (n = 11) and nondissecting thoracic aortic aneurysms confirmed by angiography or surgery. In 7 out of 9 cases, nondissecting aneurysms were detected by 2-DE, whereas in 2 patients diagnosis was established only by TEE. Three out of 6 type I dissections and 1 type II dissection could be diagnosed by tth 2-DE. But in 3 type I dissections and in all cases with type III aneurysms (n = 4) the intimal flaps and the DeBakey type of classification were identified only by TEE. In 1 patient with an extensive aneurysm of the ascending aorta and severe aortic insufficiency, a dissection was erroneously diagnosed by TEE, but not confirmed by surgery. In 1 case with type I dissection, spontaneous echo contrast within the false lumen was revealed by TEE. Complications due to TEE were not observed. Thus, in the diagnosis of thoracic aortic aneurysms and dissections the combination of tth 2-DE and TEE is superior to only tth 2-DE.