Background-This study evaluated a large group of patients enrolled in a double-blind randomized trial of the sirolimus-eluting stent to document whether the initial clinical improvement seen in previous smaller series is maintained out to 12 months and to study the potential treatment effect in patient subsets known to be at increased risk of restenosis. Methods and Results-A total of 1058 patients with de novo native coronary stenosis undergoing clinically indicated percutaneous coronary intervention were randomly assigned to sirolimus-eluting stent (533) or control bare stent (525). Procedural success and in-hospital outcomes were excellent and did not differ between the 2 groups. At 9 months, clinical restenosis, defined as target-lesion revascularization, was 4.1% in the sirolimus limb versus 16.6% in the control limb (PϽ0.001). At 12 months, the absolute difference in target-lesion revascularization continued to increase and was 4.9% versus 20% (PϽ0.001). There were no differences in death or myocardial infarction rates. In high-risk patient subsets, defined by vessel size, lesion length, and presence of diabetes mellitus, there was a 70% to 80% reduction in clinical restenosis at 1 year. Conclusions-Placement of the sirolimus-eluting stent results in continued clinical improvement at 1 year after initial implantation, with significant reduction in clinical restenosis as defined by target-lesion revascularization. Between 9 and 12 months, the absolute reduction of clinical restenosis continues to increase. Even in high-risk subsets of patients, there is a 70% to 80% relative reduction in clinical restenosis at 12 months with this drug-eluting stent.