Background: Clopidogrel and aspirin are the most popular antiplatelet agents for anticoagulation management after coronary artery bypass grafting (CABG) in clinical practice, but there is neither a standard antiplatelet therapy for patients undergoing CABG, nor an exact conclusion about its effects on graft patency until now. Methods: One-hundred and ninety-seven selected patients undergoing CABG were assigned to two groups according to antiplatelet drug: the clopidogrel group of 102 patients who received clopidogrel (75 mg) daily; and the combination group of 95 patients who received clopidogrel (75 mg) plus aspirin (100 mg) daily. Multislice computed tomography angiography was performed to evaluate graft patency at 1 month and 12 months after CABG. Results: There were no significant differences between the two groups in preoperational data. At 1 month and 12 months after CABG graft patency rates of clopidogrel group were, respectively, 99.0% and 96.9% for the left internal mammary artery (LIMA) and 98.1% and 93.5% for the saphenous vein grafts; those of the combination group were, respectively, 98.9% and 97.8% for LIMA, and 98.2% and 96.3% for saphenous vein grafts. There were no significant differences in graft patency between the two groups (p > 0.05). Conclusions: Either clopidogrel plus aspirin or clopidogrel alone maintain high graft patency in the early postoperative phase after CABG. The observed trend toward higher patency rates in patients treated with clopidogrel plus aspirin compared to those in the clopidogrel group did not reach statistical significance. © 2009 The Society of Thoracic Surgeons.