Over a five-year period (1990-1994), 72 consecutive patients were referred to transoesophageal echocardiography (TEE) on suspicion of thoracic aortic dissection. TEE was performed as the only or last investigation in 42 patients (58%). In 44 patients one or more other investigations were carried out before final clinical decision making: aortography (n = 30), X-ray computer tomography (CT, n = 18), and magnetic resonance imaging (MRI, n = 12). The final diagnosis was based on the combination of clinical information, the available examination results, and findings at surgery or autopsy; 31 of the patients were diagnosed as having aortic dissection. One patient with aortic dissection died during TEE while none of the other patients suffered major complications. The sensitivity (demonstration of dissection including correct classification in type A or B) was 81%, 80%, 45%, and 83% for TEE, aortography. CT, and MRI, respectively. The specificities were 88%, 93%, 71%, and 100%, respectively. Dissection of the thoracic aorta is a life-threatening condition demanding prompt and accurate diagnosis. None of the four techniques employed in the present study is ideal. Although TEE is adequate for immediate bedside examination our results show that more time-consuming and resource demanding investigations are sometimes required. Proper training and improved equipment may, however, increase the usefulness of TEE in patients with suspected aortic dissection.