Altered systolic blood flow in the ascending aorta has been correlated with increased aortic growth in patients with bicuspid aortic valves (BAVs). We used conventional, 2-dimensional (2D) phase contrast magnetic resonance imaging (PC-MRI) to assess the relationship between altered flow and future growth in patients with BAV. Aortic MRI data were reviewed for 17 adult patients with BAV with right-left leaflet fusion undergoing surveillance imaging who had 2D PC-MRI through their ascending aortas on an initial study, follow-up studies more than 1 year later, and an initial maximum aortic diameter of less than 4.5 cm. Diameters were measured at standard levels by 2 blinded reviewers. Normalized systolic flow displacement was calculated at peak systole from the PC-MRI data, and correlation with the interval aortic growth was performed, with adjustment for clinical/demographic factors. The average follow-up interval was 2.9 ± 1.3 years. Systolic flow displacement at the initial study strongly correlated with ascending aortic growth rate (r = 0.71, P < 0.005) with moderate, non-significant correlation between initial diameter and growth (r = 0.45, P = 0.214). Aortic growth was 4 times faster in patients with initial flow displacement of 0.2 or greater (n = 9) compared with those (n = 8) with initial flow displacement less than 0.2 (0.8 ± 0.4 vs 0.2 ± 0.3 mm/y; P = 0.002). Systolic flow displacement calculated from conventional 2D PC-MRI in the ascending aorta correlates with future aortic growth in patients undergoing routine surveillance imaging for BAV. With a cutoff valve of 0.2, flow displacement may be used to identify a subset of patients likely to have elevated growth rates and may better risk-stratify patients with BAV for aortic disease progression than vessel diameter alone.