Aim. To investigate the prognostic value of serum endogenous erythropoietin (EPO) in patients with acute coronary syndrome (ACS), including that in the development of acute kidney injury (AKI). Subjects and methods. Eighty-four patients (46 men, 38 women; mean age 63±11 years) with ACS were examined. Twenty-one (25%) patents were diagnosed with ECG ST-segment elevation acute myocardial infarction (STSEAMI), 12 (14%) had ECG non-STSEAMI, and 51 (61%) had unstable angina. Thrombolytic therapy was performed in 10 (48%) patients with STSEAMI. The patients whom had not undergone coronarography were included in the investigation to exclude the nephrotoxic effect of X-ray contrast agents. Results. AKI was observed in 7 of the patients with acute myocardial infarction and in only 1 of those with unstable angina. Four (5%) patients died during hospitalization. The EPO level of >10.5 IU/ml predicted the development of AKI in the ACS patients with a sensitivity of 71% and a specificity of 67%. That of >13.7 IU/ml was associated with hospital death in the ACS patients with a sensitivity of 100% and a specificity of 75% (AUC=0.93%). Conclusion. High serum EPO levels in an ACS patent during his hospital stay may serve as a biomarker for a high risk for AKI and high death rates.