The paper contains description of possibilities and limitations of ultrasound diagnosis in patients with acute coronary syndrome (ACS). Main attention is paid to possibilities of echocardiographic diagnosis of myocardial infarction (MI) and its complications, as well as to differential diagnostics of ACS and nonischemic conditions causing chest pain and infarction-like ECG changes. Data are presented demonstrating substantial lowering of rates of some complications of MI in patients subjected to thrombolytic therapy or interventional procedures of myocardial revascularization.