Aortic valve pathology is the most common acquired valvular heart disease in the adults of western countries, and mitral regurgitation (MR) is often clinically present in patients with degenerative aortic stenosis or insufficiency. Many studies report an incidence of MR between 65-75% in patients evaluated for aortic valve replacement. Severe aortic valve disease may be associated with functional mitral regurgitation (FMR) defined as the failure of mitral valve to prevent systolic backward flow in the absence of any significant structural or intrinsic valvular disease. Increased afterload and left ventricular remodeling have been implicated to explain FMR in patients with aortic valve disease. Moreover, organic mitral valve disease can be associated with aortic stenosis and can be rheumatic or degenerative. We have examined the data of the literature to understand the evolution of MR, the impact of mitral regurgitation on the outcome of patients undergoing aortic valve replacement, and to determine clinical predictors of prognosis in patients with concomitant MR at the time of aortic valve replacement.