Mitral annulus anatomy and dynamics were evaluated in 12 subjects using a three-dimensional transesophageal echocardiographic technique. The mitral annular area, diameters and distance from the left ventricular apex were measured in end-diastole, mid-systole, end-systole and mid-diastole. The mitral annulus had its largest area in end-systole and the smallest area in end-diastole. The shape of the annulus changed during the cardiac cycle with the maximal change occurring in the diameters passing close to the middle of the mitral leaflets. In the vertical plane, the annulus had a shallow ski-slope shape, with the attachment of the anterior leaflet being farthest from the apex. In other words, the highest point of the annulus was situated anteromedially and was visualized in the long axis imaging plane.