Aim. To study renal dysfunction in patients with myocardial infarction (MI). Subjects and methods. 670 case histories of patients diagnosed with acute coronary syndrome, including 369 (55.8%) men and 292 (44.2%) women at the age of 33 to 85 years (mean age 64.8±11.7 years), were retrospectively studied. The authors considered comorbidities and analyzed complaints, history data, and the results of physical examinations, biochemical blood tests for plasma glucose, troponin, MB fractions of creatine phosphokinase and creatinine, and cholesterol in all the patients. Instrumental studies involved electro- and echocardiography. Glomerular filtration rate (GFR) was estimated using the MDRD formula. The patients were divided into groups according to GFR values: 1) >90 ml/min/1.73 m2; 2) 60 to 89 ml/min/1.73 m2; 3) 30 to 59 ml/min/1.73 m2; 4) less than 30 ml/min/1.73 m2. Results. Most patients were found to have a moderate or significant reduction in kidney function. Worsening renal function in patients with MI was associated with advanced patient age, the lower proportion of men in the patient structure, the higher prevalence of concomitant cardiovascular diseases, such as arterial hypertension, chronic heart failure, and prior MI, and diabetes mellitus. Conclusion. The findings suggest that kidney dysfunction is of essential value in developing the multiplicity of comorbidities in patients with MI. The wide introduction of a GFR calculating method in daily medical practice will be able to adequately and timely identify renal filtration function and to make a correction into a treatment regimen, thus decreasing the number of poor outcomes.