During the planned 11 months of investigation, all patients undergoing isolated first-time coronary artery by-pass grafting will be enrolled. Patients admitted for emergency procedure, following failed percutaneous transluminal coronary angioplasty and off-pump coronary surgery, will be excluded. Because antithrombotic therapy management may differ during the postoperative period, we will exclude patients in whom a mechanical support or intra-aortic balloon pump will be required for a difficult weaning from cardiopulmonary bypass. Finally, we will exclude all patients who will not have received any oral antiplatelet agents within 5 days prior surgery, those who will have been preoperatively exposed to platelet glycoprotein IIb/IIIa inhibitors, and those with history of haematological disease. Patients treated with aspirin and clopidogrel and in whom clopidogrel will be stopped more than 5 days before surgery will also be excluded.