Background: Severe aortic regurgitation is generally associated with some degree of functional mitral regurgitation. The accompanying severe functional MR or in cases of diseased MV usually requires concomitant MV repair or replacement during AVR. However, clinical outcomes of mild to moderate functional MR after AVR is not known, information which may be important in determining future treatment strategies in patients with severe AR and functional MR. Therefore, the purpose of this study is to evaluate the change in clinical status of functional MR after AVR in patients with severe AR. Methods: A total of 158 patients with chronic aortic regurgitation undergoing AVR from 1985.2.1 ~ 2004.10.26 were enrolled in this study.(Male 108, Female 50, mean age 49.1 짹 15.2) All patients had undergone pre- and postoperative echocardiography during followup. The mean duration from initial operation to the post-operative echocardiography was 3.2 years. Functional MR was defined as MR associated with annulus dilatation and/or valve tethering without definite valvular or subvalvular structural abnormalities on echocardiography. Results: The preoperative AR severity were grade 3(n=109, 69.0%) and grade 4(n=49, 31.0%). The assessment of preoperative functional MR showed 9 patients with absence of MR(5.7%), 112 patients with mild MR(70.9%) and 37 patients with moderate MR(Grade 2 or 3, 23.4%). After AVR, improvement of MR was demonstrated in 147/158(93%). Improvement of MR by grade 1 or 2 was demonstrated in 108/112(96.4%) for grade 1 MR, 28/30(93%) for grade 2 MR and 6/7(86%) for grade 3 MR. Conclusions: Mild to moderate functional MR was associated with significant improvement after AVR in most patients with severe AR. Lone aortic valve replacement may be warranted in these subgroup of patients. Key Words : chronic aortic regurgitation, functional mitral regurgitation, aortic valve replacement