The purpose of this study is to determine if the combination of aspirin plus clopidogrel is more effective than aspirin alone in preventing another heart attack, chest pain, stroke or death in people who have already had a heart attack that was treated with fibrinolytic therapy.

Inclusion Criteria:

• STEMI within 12 hours of randomization
• Planned treatment with a fibrinolytic agent and aspirin

Exclusion Criteria:

• Intention of performing coronary angiography within 48 hours of fibrinolysis
• Treatment with clopidogrel or ticlopidine within 7 days prior to enrollment, or planned treatment with clopidogrel or ticlopidine.
• Contraindication to fibrinolysis
• Planned use of a glycoprotein IIb/IIIa inhibitor
• Prior CABG
• Evidence of cardiogenic shock or acute pulmonary edema requiring intubation or an intraaortic balloon pump
• Known renal or hepatic insufficiency