BACKGROUND: Patients with aortic stenosis (AS) treated with aortic valve replacement (AVR) may also present with associated functional mitral valve regurgitation (FMR). Whether to also address the mitral valve at the time of AVR remains unclear. This study was designed to determine the influence of MR on survival and its evolution over time. METHODS: We retrospectively reviewed 74 patients with FMR who underwent isolated AVR between 1999 and 2006 at our institution. Inclusion criteria were surgery for AVR with severe AS (mean age, 69 years; N = 47; 64% women) and FMR (grade I, 80%; grade II, 19%; grade III, 1%). Echocardiography follow-up data were obtained by mail questionnaires sent to the referring cardiologists of all survivors. All parameters were analyzed with the Kaplan-Meier method and the sign test. RESULTS: The operative mortality rate was 2%, and 9 patients (12%) died during follow-up. The mean (SD) follow-up time was 48 ± 33 months, and follow-up 96% complete. The follow-up demonstrated a decrease of FMR by 2 degrees in 3 patients (4%), and 1 degree in 14 patients (19%); regurgitation remained unchanged in the majority of patients (n = 47; 63%). FMR worsened in 10 patients overall (14%), and new-onset atrial fibrillation was found in 24 patients (33%); however, the statistical analysis failed to demonstrate an impact of worsening FMR on survival. CONCLUSION: MR in patients with severe AS and FMR at the time of AVR does not appear to worsen significantly over time. Not dealing with the mitral valve at the time of AVR might be warranted for selected patients.