Background: Clopidogrel is administered to prevent stent thrombosis. But it must be loaded before PCI. Then what about oral crushed clopidogrel just before PCI? Will it inhibit platelet aggregation earlier than whole tablet? Methods: Platelet aggregation (5 關mol/L ADP) was measured in patients undergoing elective coronary stenting. Clopidogrel was administered as a loading dose of 300 mg 24 hours before PCI (Group 1, n=4) or as crushed 300mg just before PCI (Group 2, n=4). Normal control group(n=5) was under coronary angioraphy without PCI. Results: In group 1 and 2, ADP-induced (5 關mol/L ADP) platelet aggregation was significantly inhibited 2 hours after drug administration, with maximal inhibition at 4 hours(Figure). Conclusion: A 300 mg loading lose of crushed clpoidogrel just before PCI not earlier inhibited platetet aggregation than four whole 75 mg tablets 24 hours before PCI. It may be an alternative to loading method of antiplatelet agents to minimize peri-PCI thrombotic events. The incidence of clinical event and larger number of patients require further study.