The introduction of percutaneous coronary intervention (PCI) substantially changed the treatment of patients with coronary artery disease. Stent thrombosis is the most worrisome early complication in patients undergoing PCI. Therefore, antiplatelet therapy forms an integral component of treatment with intracoronary stent implantation. A multitude of randomized and observational studies have helped identify and define the role of clopidogrel in today's PCI patient. Although much is known about its use, a number of questions still remain.