Background: Restenosis is still a clinical problem even after Sirolimus-eluting stent (SES) implantation. Several studies showed that stent fracture (SF) may be a potential cause of restenosis. We hypothesized that fractured stent strut may irritate intima uncovered by stent strut and produce late developing neointimal hyperplasia and resulting in-stent restenosis. Methods: This study consisted of 32 SFs from 19 patients who received second follow-up coronary angiography after detection of SES fracture. SFs in patients who had received balloon angioplasty or additional stent insertion at time of SF detection were excluded. We compared SF site and smallest non-SF site where each lumen diameter was the smallest except for SF site in second follow-up angiography. Results: Mean follow-up period from first angiography to second angiography was 422짹158 days. In-stent restenosis (ISR) was found in 11 (34.4 %) SFs at first angiography and 3 newly developed ISR (total 14, 43.7 %) was seen at second angiography. At first angiography, SF site and smallest non-SF site late loss was 0.52짹0.53mm and 0.35짹0.22 (p=0.039). All smallest non-SF site at second angiography did not coincide with smallest non-SF site at first angiography. SF site late loss was also significantly higher than smallest non-SF site late loss (0.51짹0.53 mm vs. 0.20짹0.21 mm; p=0.004) at second angiography (Figure). Conclusion: Neointimal hyperplasia caused by SF through local mechanical irritation and inflammation may be another cause of late developing restenosis after SES implantation.