Stenting with a sirolimus-eluting stent (SES) dramatically reduces the risk of restenosis compared to bare metal stent (BMS) implantation. However, before SES can be widely adopted in clinical practice, it is essential to conduct an economic evaluation of this effective but expensive device. Our study was undertaken to estimate the three-year cumulative medical costs of stenting using SES compared to BMS. The data on clinical sequelae of stenting using BMS were derived from our previous study, based on data collected from three Japanese hospitals. We estimated that the probability of PTCA required for revascularization would be 0.224 times in SES implantation compared than in BMS implantation based on the SIRIUS study result. The medical costs for procedures were obtained from published articles and were adjusted to the March 2005 level. Our simulation showed the expected three-year cumulative medical cost per patient to be approximately \\200,000 lower in the SES group (\\2,233,000) than in the BMS group (\\2,431,000). Sensitivity analyses with different presumptions confirmed that the economic advantage of SES over BMS was quite robust. We concluded that the use of SES would be a cost-saving option as compared with BMS implantation within the context of the Japanese healthcare system.