We assessed the diagnostic efficacy of plasma Myeloperoxidasis (MPO) alone or in combination with cardiac troponin I (cTnI) for detecting ACS in patients presenting with chest pain initiating within 24 h before the hospital admission. In this prospective cohort study were included all respondents who have visited outpatient clinic of internal diseases, University Hospital Mostar because of chest pain and suspected acute coronary syndrome within 24 h of the onset of the period of 6 months and the total sample consisted of 114 patients. Troponin and myeloperoxidase were significantly positively correlated at the beginning of treatment, myeloperoxidase was significantly positively associated with adverse cardiovascular events during hospitalization and myocardial infarction (p < 0.05), with the regression analysis did not show a significant predictor in the development of myocardial infarction (p > 0.05). Sensitivity of myeloperoxidase as a valid test detection of myocardial infarction at baseline was 0.15 and specificity was 0.85, suggesting good diagnostic value usable in the clinical practice.