Background Peri-Stent Contrast Staining (PSS) could be regarded as a relatively severe form of incomplete stent apposition. The aim of this study is to evaluate their incidence, risk factor and clinical outcomes. Materials and Methods From April 2005 to August 2008, 561 consecutive patients with 898 lesions that were treated with Sirolimus-Eluting Stent (SES) and were evaluated by follow up angiography at 10 months. The patients were divided according to with PSS (Group 1, n=23) and without it (Group 2, n=538). Major adverse cardiac events (MACE) for 3years such as cardiac death, myocardial infarction(MI), target lesion revascularization (TLR), target artery revascularization (TVR) were evaluated. Independent risk factor for PSS were elucidated by multivariate regression analysis. Results Baseline characteristics were not different. Mean follow-up duration was 937짹146 days. It was not statistically significant that cumulative MACE for 1year found 8.7% in Group 1 and 5.9% in Group 2 ( p=0.643). But, Cumulative incidence of 3years MACE was found 39.1% in Group 1 and 15.6% in Group 2 ( p=0.007 ). There was no difference in stent thrombosis between two groups for 3years ( 5.9% in Group 1 vs. 4.1% in Group 2, p=0.517). Independent risk factor of PSS was total stent length >26mm ( p=0.028, OR 2.622, C.I.1.10 to 6.19). Conclusions Long term clinical outcome of patients with PSS might be worse than those without PSS. More large clinical study will be needed. Key words : Peri-stent contrast staining, MACE, Sirolimus-Eluting Stent