This chapter about antithrombotic therapy for coronary artery disease is part of the Antithrombotic and Thrombolytic Therapy: American College of Chest Physicans Evidence-Based Clinical Practice Guidelines (8th Edition). Grade 1 recommendations are strong and indicate that the benefits do, or do not, outweigh risks, burden, and costs. Grade 2 suggestions are weaker as there is uncertainty regarding the benefits, risks and costs such that individual patients’ values may lead to different choices (for a full understanding of the grading see the “Grades of Recommendation for Antithrombotic Agents” chapter by Guyatt et al, CHEST 2008; 133[suppl]:123S–131S). Among the key recommendations are the following: for all patients presenting with non–ST-segment elevation (NSTE) acute coronary syndrome (ACS), without a clear allergy to aspirin, we recommend immediate aspirin (162 to 325 mg po) and then daily oral aspirin (75 to 100 mg) [Grade 1A]. For NSTE ACS patients who are at at least moderate risk for an ischemic event and who will undergo an early invasive management strategy, we recommend “upstream” treatment either with clopidogrel (300 mg po bolus, followed by 75 mg/d) or a small-molecule IV glycoprotein (GP) IIb/IIIa inhibitor (eptifibatide or tirofiban) [Grade 1A]. For NSTE ACS patients who are at least moderate risk for an ischemic event and for whom an early conservative or a delayed invasive strategy of management is to be used, we recommend “upstream” treatment with clopidogrel (300 mg oral bolus, followed by 75 mg/d) [Grade 1A]. For NSTE ACS patients who undergo PCI, we recommend treatment with both clopidogrel and an IV GP IIb/IIIa inhibitor (Grade 1A). We recommend a loading dose of 600 mg of clopidogrel given at least 2 h prior to planned PCI followed by 75 mg/d (Grade 1B). For all patients presenting with NSTE ACS, we recommend anticoagulation with UFH or LMWH or bivalirudin or fondaparinux over no anticoagulation (Grade 1A). For NSTE ACS patients who will undergo an early invasive strategy of management, we recommend UFH (with a GP IIb/IIIa inhibitor) over either LMWH or fondaparinux (Grade 1B). For NSTE ACS patients in whom an early conservative or a delayed invasive strategy of management is to be used, we recommend fondaparinux over enoxaparin (Grade 1A) and LMWH over UFH (Grade 1B). We recommend continuing LMWH during PCI treatment of patients with NSTE ACS when it has been started as the “upstream” anticoagulant (Grade 1B). In low- to moderate-risk patients with NSTE ACS undergoing PCI, we recommend either bivalirudin with provisional (“bail-out”) GP IIb/IIIa inhibitors or UFH plus a GP IIb/IIIa inhibitor over alternative antithrombotic regimens (Grade 1B).