Using the transesophageal approach the descending part of the aorta can be imaged by two-dimensional enchocardiography in cross sections comparable to computer tomograms. The value of combined transesophageal and transthoracic echocardiography was evaluated in 53 patients who were studied consecutively from 1983 to 1986 with symptoms of aortic dissection and compared with computed tomography, angiography, surgery and/or autopsy. In all patients the transthoracic aorta could be visualized and the dissection could be classified according to DeBakey: in 9 of 29 patients (34%) type I dissection, in 4 (14%) type II dissection and in 16 (55%) type III dissection was found. Operation was carried out because of acute symptoms in 11 of the 29 patients, and 3 additional patients died before operation. In 24 patients aortic dissection could be ruled out. A sensitivity of 97% for transthoracic and transesophageal echocardiography, of 80% for computed tomography and of 78% for angiography was calculated. The specificity for echocardiography was 100%, for computed tomography 100% and for angiography 95%. The positive predictive accuracy for echocardiography and computed tomography was 100% and 95% for angiography. The negative predictive accuracy for echocardiography was 96%, for computed tomography 77% and for angiography 79%. In no patient was an aortic dissection found by computed tomography or angiography which was not detected by echocardiography. In 1 patient with a large ectasia of the aorta ascendens aortic dissection was overlooked as retrospective analysis demonstrated. Signs of aortic insufficiency and pericardial effusion were detected.(ABSTRACT TRUNCATED AT 250 WORDS)