Platelets play a key role both in ischemic complications after percutaneous transluminal coronary angioplasty (PTCA) and in the pathogenesis of acute myocardial infarction (AMI). Until recently, there was no treatment to dissolve the platelet clot. Indeed, the plasminogen activators achieve fibrin lysis but their platelet activating side-effects and their prothrombotic effects led to failure in PTCA trials and to a significant rate of reocclusions in thrombolysis trials. A new class of platelet antagonists directed against the platelet membrane glycoprotein IIb/IIIa receptor has undergone extensive evaluation in the prevention of ischemic complications of PTCA. In contrast, its development in the treatment of AMI is just starting. This class of medications has the potential to improve clinical outcome of AMI treated either with primary angioplasty or with thrombolysis.