Antiplatelet therapy is the cornerstone of treatment for patients who present with acute coronary syndrome (ACS) or undergo percutaneous coronary intervention (PCI). Clopidogrel, in combination with aspirin, is associated with improvement in long-term clinical outcomes in these patients and is currently the antiplatelet therapy of choice. However, a significant number of patients experience recurrent ischemic events, which have been in part attributed to variability in individual response profiles to currently recommended treatment regimens. The presence of variable degrees of responsiveness, thus inadequate platelet inhibition in some patients, underscores the need for novel agents with more potency and less variable platelet inhibitory effects. Prasugrel (CS-747; LY640315), a novel third-generation oral thienopyridine, is a specific, irreversible antagonist of the platelet adenosine diphosphate (ADP) P2Y(12) receptor. Pre-clinical and early phase clinical studies have shown prasugrel to be characterized by more potent antiplatelet effects, lower interindividual variability in platelet response, and faster onset of activity compared with clopidogrel. Recent findings from large-scale Phase III testing showed prasugrel to be more efficacious in preventing ischemic events in ACS patients undergoing PCI; however, this is achieved at the expense of an increased risk of bleeding. This article reviews the currently available data regarding the efficacy and safety of prasugrel.