Aortic stenosis (AS) is the most common valvular disease and aortic valve replacement (AVR) is one of its most effective interventions. AS affects not only the left ventricle, but also vascular function beyond the stenotic valve, which can lead to various types of vascular dysfunction. However, research evaluating the effect of AS on aortic vascular function is limited. In this study, we investigated clinical meaning to evaluate endothelial function in subjects with AS. From April 2011 to April 2012, 20 consecutive adult patients with degenerative AS (mean age, 74.7 ± 7.4 years; range 50-83 years) who underwent AVR at our institution were included in the study. We measured flow-mediated dilation (FMD) to evaluate the effect of AS on endothelial function. The difference between brachial artery diameter (BAD) before (4.0 ± 0.7 mm) and after AVR (3.9 ± 0.6 mm) was not significant (p = 0.043), but FMD significantly improved after AVR (from 3.1 ± 1.8 to 6.0 ± 2.7 %, p < 0.0001). We also analyzed FMD × BAD index, endogenous vasodilatory capability independent of BAD, resulting that it also significantly increased after AVR (12.3 ± 7.0-22.5 ± 9.3, p < 0.0001). We divided patients into two groups by pre- to post-AVR change in FMD (ΔFMD); large-ΔFMD group [ΔFMD >3.0 % (median value)] and small-ΔFMD group (ΔFMD <3.0 %). There were no significant changes in age, blood pressure, heart rate, B-type natriuretic peptide, or echocardiographic parameters in either group. In contrast, BAD was significantly larger in the small ΔFMD group (4.3 ± 0.7 mm) than in the large ΔFMD group (3.7 ± 0.7 mm) (p = 0.030). In addition, cardio-thoracic ratio was significantly greater in the small ΔFMD group (58.4 ± 7.1 %) than in the large ΔFMD group (53.7 ± 4.6 %) (p = 0.048). Receiver operating characteristic curve analysis of BAD to differentiate large and small ΔFMD demonstrated an area under the curve of 0.750 (p = 0.059) and that optimal cutoff for BAD was 4.28 mm (70 % sensitivity, 80 % specificity). AVR in subjects with AS is associated with a significant improvement in FMD in the brachial artery. Measurement of the BAD may be helpful in distinguishing whether the impairment of FMD in AS derives from a stenotic valve or vascular remodeling.