This prospective study was conducted to describe the signs on transesophageal echocardiography (TEE) associated with traumatic aortic injury (TAI). Twenty-eight patients with TAI underwent TEE, and they were compared with a control group of 30 thoracic trauma patients without aortic injury. The TEE signs were classified as direct or indirect signs, and the quality of imaging was assessed. Patients' TEE images were compared with their anatomic lesions. The direct signs were thick stripes (n=19), false aneurysm (n=7), aortic dissection (n=6), free-edge intimal flap (n=15), aortic wall hematoma (n=2), fusiform aneurysm (n=13), and complete aortic obstruction (n=2). The indirect signs included minor increases in aortic diameter (n=7), impairment of the aortic Doppler color flow (n=18), and an increase of aorta-probe distance, indicating hemomediastinum (n=23). TEE allowed diagnosis of recently described limited intimal lesions frequently missed by other conventional methods, and permitted rapid diagnosis of complete rupture in which fast degeneration means that more time-consuming methods are not practicable. Significant blurring of the aortic outline was noted in 20% of cases and intraluminal artifacts were observed in 36% of cases, but neither sign impaired accurate diagnosis of TAI. The echocardiographic signs of aortic injury are complex and may be confined to a short section of the aorta. Therefore, examination by a physician highly trained in echocardiography is necessary in such cases.