Bicuspid aortic valve (BAV) is frequently associated with clinically relevant abnormalities of the aorta, suggesting the existence of a common underlying developmental defect involving the aortic valve and wall of the ascending aorta. The study aim was to evaluate noninvasively the elastic properties of the aortic root in young males with BAV, to discover whether structural abnormalities of the aorta might be manifested by impairment in elasticity.Forty-nine young male subjects with isolated BAV were consecutively detected during preenrollment military screening, and studied using transthoracic echocardiography. Data were compared with those obtained in 45 normal subjects, matched for gender and age.Patients and controls were comparable for body size, and systolic and diastolic blood pressures. BAVs were normally functioning in 18 patients (37%), and mildly regurgitant in 31 (63%). Measurements made by two-dimensional echocardiography showed that BAV patients had significantly larger aortic root dimensions at the annulus (2.4+/-0.2 versus 2.2+/-0.2 cm, p <0.001), at the sinus of Valsalva (3.3+/-0.4 versus 2.6+/-0.3 cm, p <0.001), at the sinotubular junction (2.9+/-0.3 versus 2.5+/-0.2 cm, p <0.001), and at the proximal ascending aorta (2.8+/-0.3 versus 2.5+/-0.2 cm, p <0.001). Measurements made using M-mode echocardiography at 3 cm from the annulus, showed the difference between systolic and diastolic diameters of the aortic root to be significantly smaller in patients than in controls (2.1+/-1.2 versus 3.0+/-1.1 mm, respectively, p <0.001). In patients and in controls, both aortic distensibility (2.7+/-1.5 versus 4.8+/-2.2 x 10(-6) cm2 dyne(-1), respectively, p <0.001) and aortic stiffness index (10.2+/-5.3 versus 5.03+/-1.97, respectively, p <0.001) were significantly different.Young male subjects with BAV and no or mild aortic regurgitation display large aortic size and abnormal elastic properties of the ascending aorta compared with controls. These findings confirm the notion that, in these patients, aortic root dilatation is a morphological correlate of intrinsic structural aortic abnormality.