Background and Purpose: Recently, several cases of stent fracture (SFx) have been reported and suggested as a potential mechanism of restenosis after sirolimus-eluting stent (SES). We have performed this study to evaluate the contribution of SFx to the restenosis after SES implantation. Methods: From May 2003 to June 2006, SES was implanted in 1105 lesions. During the follow up, 24 restenotic lesions were observed in 22 patients (mean age: 57.1짹8.8years, male 19). SFx was defined as the presence of strut-free space or acute misalignment of the stent compared with immediate post-procedural images of fluoroscopy. We also compared the fluoroscopic images of SES with it���s background velocity짰 stent. Results: Of the 24 SES restenosis lesions, 23 were focal (restenosis length <10mm) ISR and one had diffuse restenosis. Among the 23 focal ISR, 8 (33%) have shown SFx in in-stent segments. All of the stent fracture were developed after implantation of ��� 20 mm long SES. All fracture sites were in the middle of stents except one which was on overlap site of 2 SES. But, we couldn���t find SFx in the 30 patients with ISR after BMS implantation. Most of the cases had diffuse ISR (n=18, 60%) and 2 cases had the pattern of total occlusion, and 10 cases were focal ISR lesions. Conclusion: As compared with BMS, most lesions had the patterns of focal ISR in SES group. Also, SFx was one of the leading causes of focal ISR in the middle of the stents after SES implantation. The effective suppression of neointimal formation may be the contributing mechanism of SFx in SES.