Transesophageal echocardiography (TEE) has been used over the last 10 years (1982-1992) to study the heart and thoracic aorta. We set out to evaluate the diagnostic applications of TEE in patients with thoracic trauma. Specifically, TEE was performed on patients suspected of having either a cardiac contusion or an injury of the thoracic aorta. Fifty-eight patients admitted with thoracic trauma underwent TEE. Fifty of those patients suspected of having a cardiac contusion also underwent transthoracic echocardiography (TTE). The two diagnostic modalities were compared. In 21 of these patients a wide mediastinum was apparent on admission chest x-ray films. Nineteen of this latter group underwent thoracic angiography in addition to TEE. Two patients underwent post-mortem examination. Of the 50 patients undergoing both TEE and TTE, a cardiac contusion was detected by TEE in 26 patients. Transthoracic echocardiography detected only six contusions in this group. Of the 21 patients with a wide mediastinum, TEE detected three obvious aortic disruptions. These findings were confirmed in each case by angiography. In 16 cases TEE showed the aorta to be normal. This was confirmed on the angiogram in 14 cases and by autopsy in two cases. Transesophageal echocardiography revealed an aortic intimal irregularity distal to the left subclavian artery in two cases. The results of aortography were normal in these last two cases. As a diagnostic modality, TEE more accurately detected cardiac contusions than TTE (p less than 0.001) and was a very sensitive screening tool in the early evaluation of patients with a wide mediastinum.