The use of dual antiplatelet therapy is considered standard of care in patients post percutaneous coronary intervention (PCI) with stenting. However, a significant proportion of patients is considered clopidogrel resistant and this resistance is shown to be accompanied by future adverse events. Additionally, clopidogrel resistance has been linked with the CYP2C19 polymorphism. The hypothesis of the study is to define in consecutive patients undergoing PCI those that are clopidogrel resistant PCI following routinely used loading as estimated predischarge with the VerifyNow point of care system of platelet reactivity. Clopidogrel resistant patients will be randomized in 1:1 fashion to prasugrel 10 mg or clopidogrel 150mg daily. Platelet reactivity will be assessed at day 30, when treatment crossover will be performed. At day 60 platelet reactivity will be determined as well. In addition, in all patients genetic determination of CYP polymorphisms (including the CYP2C19)known to affect clopidogrel metabolism will be performed.