Recent studies have reported circulating microRNAs (miRNAs) as novel biomarkers for cardiovascular diseases including acute myocardial infarction, heart failure, diabetes mellitus, stroke, and acute pulmonary embolism. The aims of this study were 1) to compare the plasma expression levels of miRNAs in patients with acute coronary syndrome (ACS) and control subjects and in ST-elevation myocardial infarction (STEMI) and non-STEMI 2) to evaluate miRNAs potential to be used as novel diagnostic biomarkers for ACS. Twenty seven consecutive patients, admitted to emergency department of a training and research hospital between January-December 2013 with acute chest pain and/or dyspnea and diagnosed with ACS, and 16 non ACS control subjects were included in this study. miRNA profiling was performed by using real time polymerase chain reaction. Functions of dysregulated miRNAs were evaluated by computerized-pathways analysis. miR-221-3p was one of the two most dysregulated miRNAs with a fold regulation of 3.89. It was significantly positively correlated with both Troponin and GRACE and Synthax Score. Moreover, miR221-3p was found to be significantly inversely correlated with left ventricular ejection fraction. miR-221-3p was the most prominent biomarker candidate with an area under curve (AUC) level of 0.881 (95% confidence interval: 0.774-0.987; p = 0.002). The present study is the first to report an increased expression levels of miR-221-3p in AMI. Since miR-221-3p has a high discriminative value and significant relations with Troponin, GRACE and Synthax score and left ventricular systolic function, it may be a potential biomarker for early prediction of AMI. (C) 2016 Elsevier B.V. All rights reserved.