Echocardiography was used for the examination of 45 patients with rheumatic mitral valve insufficiency. Echocardiographic data were found to permit making the diagnosis of mitral valve disease and differentiating within the group of mitral valve disease as such. A mitral disease with prevailing insufficiency is characterized on an echocardiogramme by a unidirectional diastolic movement of thickened mitral cusps, by an increased general excursion of the mitral valve, dilatation of the left ventricular cavity, increased systolic excursion of the ventricular septum, and a significant dilatation of the left atrial cavity. "Pure" mitral insufficiency is characterized by a dilatation of the left heart, vari-directional movements of the mitral cusps during the diastole, and a marked lack of their closure during the systole.