IMPORTANCE: Despite antirestenotic efficacy of coronary drug-eluting stents (DES) compared with bare metal stents (BMS), the relative risk of stent thrombosis and adverse cardiovascular events is unclear. Although dual antiplatelet therapy (DAPT) beyond 1 year provides ischemic event protection after DES, ischemic event risk is perceived to be less after BMS, and the appropriate duration of DAPT after BMS is unknown. OBJECTIVE: To compare (1) rates of stent thrombosis and major adverse cardiac and cerebrovascular events (MACCE; composite of death, myocardial infarction, or stroke) after 30 vs 12 months of thienopyridine in patients treated with BMS taking aspirin and (2) treatment duration effect within the combined cohorts of randomized patients treated with DES or BMS as prespecified secondary analyses. DESIGN, SETTING, AND PARTICIPANTS: International, multicenter, randomized, double-blinded, placebo-controlled trial comparing extended (30-months) thienopyridine vs placebo in patients taking aspirin who completed 12 months of DAPT without bleeding or ischemic events after receiving stents. The study was initiated in August 2009 with the last follow-up visit in May 2014. INTERVENTIONS: Continued thienopyridine or placebo at months 12 through 30 after stent placement, in 11,648 randomized patients treated with aspirin, of whom 1687 received BMS and 9961 DES. MAIN OUTCOMES AND MEASURES: Stent thrombosis, MACCE, and moderate or severe bleeding. RESULTS: Among 1687 patients treated with BMS who were randomized to continued thienopyridine vs placebo, rates of stent thrombosis were 0.5 vs 1.11 (n = 4 vs 9; hazard ratio [HR], 0.49; 95 CI, 0.15-1.64; P = .24), rates of MACCE were 4.04 vs 4.69 (n = 33 vs 38; HR, 0.92; 95 CI, 0.57-1.47; P = .72), and rates of moderate/severe bleeding were 2.03 vs 0.90 (n = 16 vs 7; P = .07), respectively. Among all 11,648 randomized patients (both BMS and DES), stent thrombosis rates were 0.41 vs 1.32 (n = 23 vs 74; HR, 0.31; 95 CI, 0.19-0.50; P <.001), rates of MACCE were 4.29 vs 5.74 (n = 244 vs 323; HR, 0.73; 95 CI, 0.62-0.87; P <.001), and rates of moderate/severe bleeding were 2.45 vs 1.47 (n = 135 vs 80; P <.001). CONCLUSIONS AND RELEVANCE: Among patients undergoing coronary stent placement with BMS and who tolerated 12 months of thienopyridine, continuing thienopyridine for an additional 18 months compared with placebo did not result in statistically significant differences in rates of stent thrombosis, MACCE, or moderate or severe bleeding. However, the BMS subset may have been underpowered to identify such differences, and further trials are suggested. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00977938.