Clopidogrel non-responsiveness is probably multifactorial; several genetic and non genetic factors may contribute to impaired platelet inhibition by clopidogrel. In this regard, it is meaningful to determine genetic polymorphisms contributing to the variability of clopidogrel response in patients with Coronary Artery Disease (CAD). In fact, the recognition of these factors might predict the exposure to the risk of thrombosis and cardiovascular death in these patients. Therefore, the goal of this study is to determine the impact of the polymorphisms, affecting CYP2C19, ABCB1, PON1 and P2RY12 genes, on the response to clopidogrel in patients with CAD.