Functional mitral regurgitation (FMR) is the mitral regurgitation that occurs due to myocardial disease in the presence of normal mitral valve leaflets. This scenario has the different characteristics than the organic mitral regurgitation. Functional mitral regurgitation is a disease of the ventricle and occurs by the deformation of the mitral valve leaflets. This morbid entity is frequent and has bad prognosis. Functional mitral regurgitation is the result of complex pathophysiologic process including left ventricular local and global remodeling, mitral annular and papillary muscle dysfunction, and left ventricular dysfunction. The dynamic behavior of FMR complicates the quantification of the regurgitation. Exercise stress echocardiography is of particular importance in the evaluation of the hemodynamic burden of FMR. Particular pathophysiological properties of the FMR necessitate different therapeutic approaches than the current ones for classical mitral regurgitation.