Background and Objectives: Despite several case reports of stent fracture after sirolimus-eluting stent (SES) implantation, clinical characteristics and implications have not been well known. Methods : Clinical records and angiographic films of patients who received follow-up coronary angiography between February 2005 and July 2006 were retrospectively analyzed. Results : Of the 1614 stents implanted in 899 patients, follow-up angiography was performed in 578 patients (1001 stents). 17 (1.7 %) stents were found to have 21 stent fractures. Twelve stent fractures were proved with coronary angiography and intravascular ultrasound while others were proved with only angiography. Sixteen fractures occurred at right coronary artery which was more moving than other arteries. Three and 2 fracture were seen at left circumflex artery and left anterior descending artery respectively. All stent fractures were observed in longer stents (28 mm to 81 mm) covering longer vessel. Twelve (57%) stent fractures occurred around areas of increased rigidity due to metal overlapping or bifurcation stenting that might have acted as a fulcrum. Extreme (> 90o) or moderate (45o-90o) angulation was associated with 7 (39%) or 12 (57%) stent fractures respectively. Stent : maximal inflation balloon size ratio (1.06) was not so high as expected. Surprisingly, in-stent restenosis occurred in only two (10%) stent fractures where left main bifurcation stenting was performed. Conclusions : SES stent fracture may be related with vessel movement, stent length, angulation and increased stent rigidity. However, clinical implication may be not so significant as expected.