The level of blood plasma selenium was analyzed by microfluorimetric method in in-patients and out-patients with acute coronary syndrome with ST-elevation resulting in acute Q-wave myocardial infarction. 72 patients, 40-75 years old, with acute Q-wave myocardial infarction were followed during a month. The initial decreased concentration of blood plasma selenium was recorded in most patients in the acute period of the myocardial infarction: deficiency of the microelement (< 90 mcg/l) was found in 30 subjects, the critical ranges (< 70 mcg/l) were stated in 33 patients. Just 2 patients had optimal concentration and 7 patients had a suboptimal one (90-114 mcg/l). Blood plasma level of the microelement increased in 2 weeks after myocardial infarction (in subacute stage) but it was still within deficient or critical levels. No difference was detected in selen concentration depending on gender, age, location on myocardial infarction, accompanying diseases, presence of some risk factors (smoking, alcohol abuse, hereditary predisposition to coronary artery disease). At the same time we revealed a significant Spearman rank correlation in patients with Q-wave myocardial infarction between basal level of blood serum selenium on the one hand, and electrocardiography indices (reflecting the rate of myocardial lesion and necrosis), echocardiography. data (which characterize myocardium reparation processes and remodeling), CPK (a prognostic marker of the myocardial necrosis), HDL-cholesterol (lipid profile index), blood potassium level and BMI on the other.