The risk of adverse events in patients with acute coronary syndrome remains substantial despite the use of regular aspirin. The addition of clopidogrel to regular aspirin therapy has been shown to be associated with significantly better outcomes in a variety of clinical settings within the spectrum of acute coronary syndromes. In this article, the evidence and therapeutic implications for the use of clopidogrel in patients with non-ST-elevation and ST elevation acute coronary syndromes is discussed, and also in those undergoing percutaneous coronary intervention. The use of clopidogrel in combination with other antithrombotics in the acute setting is considered, including glycoprotein IIb/IIIa receptor antagonists and direct thrombin inhibitors. Clopidogrel has changed the way in which patients with non-ST-elevation and, more recently, ST elevation acute coronary syndromes are treated.