To investigate the prognostic role of erythropoietin (EPO) in patients with acute coronary syndrome (ACS). Eighty-four patients (46 men, 38 women, mean age 63+/-11 years) with ACS were studied. Twenty-one patients had ST-elevation myocardial infarction (STEMI), 12 - non-ST-elevation myocardial infarction, 51 - unstable angina (UA). Ten patients with STEMI received thrombolytic therapy. Coronary angiography during hospitalization was criterion for exclusion from the study. Serum EPO was measured at hospital admission. In-hospital mortality was 5%. Median EPO serum level was higher among patients who died (78.1 [27.8-143.5] vs. 9.0 [6.4-14.1]I.U./ml, p=0.004). Acute kidney injury (AKI) was observed in 7 patients with myocardial infarction (21%) and only in 1 with UA.EPO >10.5 I.U./ml was a significant predictor of AKI development (area under curve 0.73; sensitivity 71%, specificity 67%). The results of the present study indicate that in patients with ACS admission serum level of EPO may be an important biomarker of development of AKI and in-hospital mortality.