The aim of this study was to investigate the value of tissue Doppler imaging (TDI) using transesophageal echocardiography (TEE) in assessing the elastic properties of the thoracic aorta in patients with Marfan's syndrome. Aortic distensibility, stiffness index, and pulse-wave velocity were calculated using M-mode data in a TEE short-axis view in 31 patients with Marfan's syndrome and 22 normal controls. Acceleration time, maximum wall expansion velocity (Vmax), and wall strain were determined from TDI tracings. Indexes derived from TDI differed at a greater level of significance than M-mode-derived indexes in patients with dilated and normal aortas. Significant predictors of aortic dilation were systolic blood pressure, aortic stiffness index, Vmax, and strain. Decreased aortic strain and Vmax and increased stiffness index were predictive of aortic dissection (odds ratios 4.5, 3.3, and 2.2). In conclusion, the TDI assessment of aortic wall mechanics is complementary to standard M-mode measurements in discriminating normal subjects from patients with Marfan's syndrome and is accurate in predicting aortic dilation and dissection.