Background: Celecoxib, cyclooxygenase (COX)-2 inhibitor, has been reported to inhibit neointimal hyperplasia in animal studies and to reduce restenosis after coronary stenting in COREA-TAXUS clinical trial. However, it is not known whether the administration of celecoxib would weaken antiplatelet effects of aspirin and clopidogrel which are used after stenting. Methods: We recruited healthy volunteers (n=40) and randomized them into five subgroups. Each subject received the medication for 6 days and blood samples were taken day 0 and 7. Celecoxib 200mg twice a day, and/or aspirin 100mg daily, and/or clopidogrel 75 mg daily was administered. We compared platelet function by using light transmittance aggregometry and arachidonic acid metabolite assay among subgroups. Results: Celecoxib single treatment did not affect platelet aggregation. Dual asprin and Plavix treatment inhibited platelet aggregation by 53%, which was not affected by addition of celecoxib showing 52% inhibition (t-test: p=0.873). The changes of prostacyclin level did not differ among each treatment group (ANOVA: p=0.193). Statistically not significant, celecoxib seems to lower the thromboxane level further when added to antiplatelet agents. Conclusion: Celecoxib treatment did not interfere with antiplatelet effect of aspirin or clopidogrel, suggesting that celecoxib as anti-restenosis agent would be administered safely during coverage of dual antiplatelet therapy in patients with coronary stenting without increasing thrombogenecity.