Background: Heavy metal ions can cause allergic and inflammatory reactions that might be associated with in-stent restenosis. This randomized multicenter clinical study was designed to determine if carbon ion-implanted stents reduce luminal late loss by blocking heavy metal ion diffusion into the surrounding tissue. Methods: A total of 225 patients with 230 native coronary lesions were randomly assigned to receive either a carbon ion-implanted ArthosInert stent(group 1, n=113) or a bare metal Arthos stent(group 2, n=117). The primary endpoint was in-stent luminal late loss at 6-month angiographic follow-up, and the secondary endpoints were the 6-month angiographic restenosis rate and the occurrence of the major adverse cardiac events(MACE) including death, nonfatal myocardial infarction, and target lesion revascularization at 12 months. Results: The baseline characteristics were similar in the 2 groups. In-hospital events did not occur in any patients. Angiographic follow-up at 6 months was obtained in 184 lesions(80%). At follow-up, the luminal late loss was similar in the 2 groups(0.91±0.77mm in group 1 vs 0.88±0.80 mm in group 2, P=.79), and the angiographic restenosis rates were 11.0%in group 1 and 16.1%in group 2(P=.31). The occurrence rates of MACE at 12 months were 9.1%in group 1 and 10.4%in group 2(P=.73). Conclusions: The initial and long-term outcomes of the carbon ion-implanted stent were excellent. However, it did not improve long-term outcomes vs the bare metal stent. Background: Heavy metal ions can cause allergic and inflammatory reactions that might be associated with in-stent restenosis. This randomized multicenter clinical study was designed to determine if carbon ion-implanted stents reduce luminal late loss by blocking heavy metal ion diffusion into the surrounding tissue . Methods: A total of 225 patients with 230 native coronary lesions were randomly assigned to either either carbon-implanted Arthroshire stent (group 1, n = 113) or a bare metal Arthos stent (group 2, n = 117) primary endpoint was in-stent luminal late loss at 6-month angiographic follow-up, and the secondary endpoints were the 6-month angiographic restenosis rate and the occurrence of the major adverse cardiac events (MACE) including death, nonfatal myocardial infarction, and Target: lesion revascularization at 12 months. Results: The baseline characteristics were similar in the 2 groups. In-hospital events did not occur in any patients. Angiographic follow-up at 6 month At follow-up, the luminal late loss was similar in the 2 groups (0.91 ± 0.77 mm in group 1 vs 0.88 ± 0.80 mm in group 2, P = .79), and The angiographic restenosis rates were 11.0% in group 1 and 16.1% in group 2 (P = .31). The occurrence rates of MACE at 12 months were 9.1% in group 1 and 10.4% in group 2 (P = .73). Conclusions: The initial and long-term outcomes of the carbon ion-implanted stent were excellent. However, it did not improve long-term outcomes vs the bare metal stent.