The mitral valve is the most complex of the cardiac valves. Its leaflets are unequal in size: one is continuous with the left atrial endocardium and the other with the aorta. The valve contains about 120 chordae tendineae connecting the leaflets to myocardial pillars (papillary muscles), which in turn are continuous with the left ventricular free wall. It has only a partial anulus fibrosis (only at the base of the posterior mitral leaflet). Since the mitral valve connects with the left atrial wall via the mural endocardium, conditions affecting this chamber also may affect mitral function. This review surveys conditions involving the mitral anulus, leaflets, chordae tendineae, papillary muscles, and left ventricular free wall that may cause this valvular orifice to be either stenotic or incompetent, or both.