Background: Elastic properties of aorta have been known to be abnormal in patients with coronary artery disease (CAD). However, aortic distensibility (AD), one of the elasticity indexes, has not been ascertained whether it is independently associated with CAD. Methods: We prospectively enrolled 305 subjects (102 patients with CAD and 193 patients without it) among 373 consecutive patients undergoing coronary angiography for the assessment of suspected CAD. Patients with acute coronary syndrome, previous myocardial infarction, valvular heart disease more than mild, atrial fibrillation, history of coronary intervention or surgery and creatinine > 2mg/dl were excluded. Aortic diameters were measured at a level 3 cm above the aortic valve using echocardiography. AD (cm2 X dyn-1 X 10-6) was calculated from the aortic diameters and brachial artery pressure using the formula: 2 x (change in aortic diameter)/(diastolic aortic diameter) x (change in blood pressure). Results: Systolic, diastolic blood pressure and pulse rate were similar in both CAD and non-CAD patients. AD was significantly lower in patients with CAD than those without CAD (3.00짹0.25 vs 1.15짹0.30, p<0.001). In multivariate analysis, AD remained significantly associated with CAD (p<0.001) after adjustment for age, gender, hypertension, diabetes and antihypertensive drug therapy. Moreover, AD showed significant inverse relationship with the severity of CAD, expressed as one-, two-, and three-vessel disease (p<0.001). Conclusions: Our findings suggest that impaired AD is an independent risk marker for CAD, as well as significantly associated with the severity of CAD.