Antiplatelet therapy is a cornerstone of the management of patients with acute coronary syndromes or for those undergoing percutaneous coronary intervention. As the intricacies of platelet biology and mechanisms of thrombus formation are revealed, novel antiplatelet therapies have emerged. Bleeding risk, however, has grown in concert with more potent platelet inhibition. This article reviews platelet biology and receptors to provide a foundation for understanding of antiplatelelet therapy. It also highlights recent advances in antiplatelet therapy, with a focus on mechanisms of action, pharmacodynamic data, and the balance of thrombotic versus bleeding outcomes.