Progression of asymmetric dilated aorta associated with bicuspid aortic valve (BAV) is difficult to evaluate conventionally. The aim of the study was to calculate the rate of progression of the dilated BAV aorta after aortic valve replacement (AVR) using a 3-dimensional (3-D) reconstruction tool.Methods and Results:Fourteen stenotic BAV and 14 stenotic tricuspid aortic valve (TAV) patients with mildly dilated ascending aorta were reviewed. A patient-specific 3-D aortic model was reconstructed from preoperative and postoperative computed tomography data (BAV, 2.5±1.9 years after AVR; TAV, 2.2±1.8 years after AVR). Aortic diameter, including the longest and shortest, was measured on the maximum perpendicular cross-section tangential to the 3-D centerline of the reconstructed model. The longest diameter was defined as that passing through the distal point of the greater curvature of the aorta. The shortest diameter was defined as perpendicular to the longest. The progression rates were compared between the BAV and TAV groups. The progression rate of ascending aortic diameter was greater for BAV (longest diameter, 1.02±1.03 vs. -0.075±0.78 mm/year, P<0.001; shortest diameter, 0.41±0.62 vs. -0.016±0.59 mm/year, P=0.003). The longest diameter of the proximal arch also grew more rapidly in the BAV group (P<0.001).