Backgroud: Triple antiplatelet therapy with cilostazol has been known to be superior to dual antiplatelet therapy in the era of 1st generation DES in terms of clinical outcome. However, it remains to be cleared whether triple antiplatelet therapy also has similar efficacy after everolimus-eluting stent (EES) implantation in the era of 2nd generation DES. Methods:In CO-ACT registry, the study subjects were 970 patients who underwent PCI with EES (Xience V or Promus) and were analyzed retrospectively. The patients were divided into 2 groups: those treated with triple antiplatelet drugs (aspirin, clopidogrel, and cilostazol; group A, n=231, M=140 (60.6%), mean age=63.8짹11.9 years) and those with dual antiplatelet drugs (aspirin and clopidogrel; group B, n=739, M=477 (64.5%), mean age=63.8짹11.1 years). The incidences of various clinical outcomes were compared between group A and B at 2 years after index PCI. Results: There was no significant difference in the incidence of major bleeding between 2 groups. Compared with group B, group A showed no significant difference of cardiac death and MI (adjusted odds ratio, 1.826; 95% CI, 0.620-5.379; p=0.274), MACE (cardiac death, MI and TLR) (adjusted odds ratio, 1.483; 95% CI, 0.778-2.826; p=0.231) and Target vessel failure (cardiac death, MI and TVR) (adjusted odds ratio, 1.001; 95% CI, 0.430-2.328; p=0.999). Conclusions: Triple antiplatelet therapy has no beneficial effect in clinical outcome compared to dual antiplatelet therapy in patients with EES implantation.