Background Dilatation of the ascending aorta in aortic stenosis may be partly explained by intrinsic wall structure changes, but the relative contribution of altered hemodynamics is unclear. The aim of this study was to assess the association between ascending aortic dimensions and valve stenosis severity. Methods and Results An analysis of echocardiographic examinations was conducted in 296 patients with aortic stenosis (179 males, mean age 71 years), 57 with bicuspid and 239 with tricuspid aortic valve, mean transaortic gradient 43±20 mmHg, and not more than moderate aortic regurgitation. Aortic dimensions at the level of annulus, sinuses of Valsalva, sinotubular junction and proximal ascending aorta were measured. Only height (p<0.001), degree of aortic regurgitation (p<0.01) and presence of bicuspid aortic valve (p<0.001) were independent predictors of ascending aortic dimensions. Conclusions An independent association between aortic pressure gradients and proximal ascending aortic dimensions was not observed in patients with bicuspid or tricuspid aortic valve stenosis. Therefore, the poststenotic dilatation of the ascending aorta is not explained by aortic stenosis severity itself. Possible nonhemodynamic causes deserve detailed study at the time of diagnosis. (Circ J 2007; 71: 84 - 88)