Dual anti-aggregant therapy is recommended standard of therapy applicable to all patient groups undergoing PPCI. The aspirin-clopidogrel regiment is signed to every patient without assessing therapeutic effect. In face of growing evidence of platelet resistance to the standardized therapy there is a demand for reliable diagnostic tool for rapid and accurate assessment of platelet reactivity. TEG is an established technique to assess the quality of clot formation' used mainly in surgery and obstetrics to determine possible bleeding diathesis. Recently it became to be used in cardiology, where it can be a valuable tool to assess a response to antiplatelet therapy and its association with the outcome. However, there is a few data about use of TEG in STEMI patients undergoing PCI. Our study is designed to assess by TEG the platelet's response to clopidogrel treatment during acute STEMI in patients undergoing primary PCI and the correlation of this response with the long term outcome.