Myocardial infarction (MI) developed in 9% of 230 patients with active infectious endocarditis. Development of MI was associated with worsened clinical course and poorer prognosis of infectious endocarditis. MI manifested with pain in 43 and was painless in 57% of these cases. In 29% of patients initial manifestations of MI were disturbances of cardiac rhythm and conduction, and acute left ventricular failure. This precluded timely electrocardiographical diagnosis. However repetitive ECG recordings allowed to confirm MI in all patients. Elevation of enzymes helped to diagnose MI in 81% of cases. Possible causes of MI were shutting of coronary artery ostium by vegetation from an aortic valve cusp (in 47%) and/or lowering of perfusion pressure in coronary arteries because of severe aortic insufficiency (in 62% of patients). Disturbances of hemostasis with activation of its vascular and platelet elements and hypercoagulation found in all patients with infectious endocarditis also facilitated development of MI. The data obtained explain under investigated sides of pathogenesis of MI in infectious endocarditis and allow to find ways for improvement of its diagnosis and therapy.