BACKGROUND: Bioresorbable vascular scaffolds were developed to overcome the shortcomings of drug-eluting stents in percutaneous coronary intervention (PCI). We performed an investigator-initiated, randomized trial to compare an everolimus-eluting bioresorbable scaffold with an everolimus-eluting metallic stent in the context of routine clinical practice. METHODS: We randomly assigned 1845 patients undergoing PCI to receive either a bioresorbable vascular scaffold (924 patients) or a metallic stent (921 patients). The primary end point was target-vessel failure (a composite of cardiac death, target-vessel myocardial infarction, or target-vessel revascularization). The data and safety monitoring board recommended early reporting of the study results because of safety concerns. This report provides descriptive information on end-point events. RESULTS: The median follow-up was 707 days. Target-vessel failure occurred in 105 patients in the scaffold group and in 94 patients in the stent group (2-year cumulative event rates, 11.7% and 10.7%, respectively; hazard ratio, 1.12; 95% confidence interval [CI], 0.85 to 1.48; P=0.43); event rates were based on Kaplan-Meier estimates in time-to-event analyses. Cardiac death occurred in 18 patients in the scaffold group and in 23 patients in the stent group (2-year cumulative event rates, 2.0% and 2.7%, respectively), target-vessel myocardial infarction occurred in 48 patients in the scaffold group and in 30 patients in the stent group (2-year cumulative event rates, 5.5% and 3.2%), and target-vessel revascularization occurred in 76 patients in the scaffold group and in 65 patients in the stent group (2-year cumulative event rates, 8.7% and 7.5%). Definite or probable device thrombosis occurred in 31 patients in the scaffold group as compared with 8 patients in the stent group (2-year cumulative event rates, 3.5% vs. 0.9%; hazard ratio, 3.87; 95% CI, 1.78 to 8.42; P<0.001). CONCLUSIONS: In this preliminary report of a trial involving patients undergoing PCI, there was no significant difference in the rate of target-vessel failure between the patients who received a bioresorbable scaffold and the patients who received a metallic stent. The bioresorbable scaffold was associated with a higher incidence of device thrombosis than the metallic stent through 2 years of follow-up. (Funded by Abbott Vascular; AIDA ClinicalTrials.gov number, NCT01858077 .).