Background: The aim of the present study was to investigate the long-term outcome of sirolimus-eluting stent (SES) implantation in lesions with severe calcification that may disturb adequate stent expansion and increase the risk of restenosis and target lesion revascularization (TLR). Methods and Results: The Cypher Post-Marketing Surveillance Registry study has been conducted since August 2004 in Japan to evaluate the efficacy and safety of SES in a real-world setting. Data on 2,458 lesions in 2,050 patients were reviewed, and the angiographical outcomes at 240 days and clinical outcomes at 1,080 days after implantation compared between calcified lesions and non-calcified lesions in dialysis patients and non-dialysis patients. In non-dialysis patients, the rates of major adverse cardiac events (MACE; 16.0% vs. 12.8%; P=0.144) including TLR (4.9% vs. 6.0%; P=0.457), and restenosis (10.1% vs. 7.8%; P=0.207) were similar in calcified lesions and non-calcified lesions. In dialysis patients, the rate of MACE was similar in calcified lesions and non-calcified lesions (51.1% vs. 43.1%; P=0.544), but the rates of TLR (29.8% vs. 9.8%; P=0.020), and restenosis (39.5% vs. 17.0%; P=0.029) were significantly higher in calcified lesions than in non-calcified lesions. Conclusions: There is a differential impact of calcification on the long-term outcome of SES implantation in dialysis and non-dialysis patients. (Circ J 2012; 76: 57-64)