Between September 1987 and April 1989, forty patients suspected to have aortic dissection were evaluated by transesophageal echocardiography. Aortic dissection was identified in 18 patients. This study evaluated the ability of transesophageal echocardiography in the assessment of the 22 patients in whom aortic dissection was not found. A range of pathologic conditions was diagnosed in these patients. Five patients had ischemic heart disease when they were initially seen. Among the remaining 17 only one patient had a normal aorta. Aortic disease was present in the other 16 patients with aortic dilatation in 10. Atheromas were detected in seven patients with concomitant aortic dilatation in five of them. An extrinsic aortic mass was present in two patients. Transesophageal echocardiography correctly identified an anastomotic leak at the site of left coronary artery implantation in a patient with a recent Bentall procedure, and a large mobile clot within the proximal descending aorta in a patient with blunt chest trauma. These findings obviated the need for other tests in 15 patients and led to surgery in four with no ancillary tests performed in three of them. Thus transesophageal echocardiography has an important role in assessing patients with suspected dissection. Aortic disease is common even in patients in whom aortic dissection is excluded, and some of the conditions can be just as life-threatening as dissection. Transesophageal echocardiography not only reliably identifies dissection but can also detect luminal and extraluminal diseases not adequately visualized by other modalities.