The ISR-DAPT Study is a multicenter, randomized controlled trial that will enroll 1000 subjects treated with percutaneous coronary intervention (PCI) for in-stent restenosis. All patients will be randomized to receive either 12 months or 24 months of dual antiplatelet therapy with a P2Y12 receptor antagonist in addition to aspirin after index procedure. All patients continue receiving aspirin indefinitely. The primary efficacy end points of this study are the incidence of a composite end point including all cause deaths, myocardial infarction, the incidence of Academic Research Consortium defined definite or probable stent thrombosis and stroke (MACCE) at 24 months. The primary safety end point is the incidence of GUSTO moderate or severe bleeding at 24 months.