Echocardiography was conducted in patients who had suffered from myocardial infarction (47 were examined in the subacute period of myocardial infarction and 23 in more remote periods) with signs of mitral insufficiency and 31 patients with no signs of mitral insufficiency (they were examined in the subacute period of myocardial infarction). It was found that after myocardial infarction the contractility of the heart muscle is diminished to a greater extent in patients with signs of mitral insufficiency than in the others. In patients with mitral insufficiency symptoms of circulatory insufficiency were revealed more frequently. The mechanisms of the development of mitral insufficiency in patients with myocardial infarction are discussed.