Backgrounds Previous studies have demonstrated that blood sirolimus levels are elevated after sirolimus-eluting stent implantation. In experimental animal studies, oral sirolimus (systemic low dose of sirolimus) have been shown to inhibit smooth muscle cell proliferation during the arterial response to injury. We investigated whether systemic effect of sirolimus-eluting coronary stent (DES) may inhibit in-stent restenosis (ISR) on simultaneously implanted bare metal stent (BMS) in multivessel coronary artery disease patients. Methods Between February 2003 and August 2004, 91 patients (mean age 62짹10 yrs, male 58) with multiple coronary lesions underwent stenting with DES and BMS simultaneously. We followed all patients clinically for mean period of 8짹7months and angiographic follow up was currently performed in 28 patients at 7짹2months after coronary intervention. Primary end point was defined as re-hospitalization due to cardiovascular events and target vessel revascularization. Results Overall DES was implanted in 116 lesions (diameter: 3.10짹0.31, length: 25.3짹6.1) and BMS implanted in 110 lesions (diameter: 3.29짹0.53, length: 18.48짹5.2). The rate of binary ISR was 14.2% (4/28: 1 total ISR and 3 diffuse ISR) in the BMS implanted lesion and 3.5% (1/28: 1 proximal edge restenosis) in the DES lesion. The late loss was 0.82짹0.83mm in the BMS implanted lesions. The overall rate of MACE was 3.2% (3/91: 2 re-hospitalization due to chest pain and 1 sudden cardiac death) in the study group. Conclusions Bare metal stent implanted simultaneously sirolimus-eluting stent showed tendency for lower in-stent restenosis rate and late loss compared with previous reported datas concerning bare metal stents. The results of this study suggest that the systemic effect of sirolimus after DES deployment may have a significant effect on neointimal proliferation of simultaneously deployed bare metal stents.