Aortic root dilation has been previously reported to be associated with aortic stenosis (AS), but data to support this statement are scarce. The dimensions of the aortic root were measured at 4 levels (annulus, sinuses, sinotubular junction, and ascending aorta) in 88 patients (mean age 71.2+/-9.7 years; 56% men) with severe AS who underwent intraoperative transesophageal echocardiography immediately before aortic valve replacement. These patients were compared with 76 gender- and age-matched patients without AS who underwent transesophageal echocardiography for various indications. The etiology of aortic valve stenosis was degenerative in 62 (70.5%), bicuspid aortic valve (BAV) in 15 (17.0%), and rheumatic in 11 (12.5%). The ascending aorta was significantly wider in AS with various etiologies (BAV, rheumatic, degenerative) than in the controls (39+/-6.9, 35.0+/-4.2, 33.1+/-4.1, and 31.3+/-3.7 mm, respectively; p<0.001). The dimensions of the sinuses and sinotubular junction were significantly less in those with AS of degenerative etiology than in the controls (29.5+/-4.0 vs 32.5+/-4.3 mm and 23.6+/-3.0 vs 26.8+/-3.0 mm, respectively, p<0.001). The prevalence of a dilated aorta (>37 mm) was 3.9%, 13.1%, 36.4%, and 60% in the control group and AS patients with degenerative, rheumatic, and BAV etiology, respectively (p<0.0001). In conclusion, patients with severe AS due to BAV had significant dilation of the aortic root. Patients with degenerative and rheumatic etiology had less remarkable dilation compared with control group, and most values were within the normal range.