The incidence of recurrent ulcer bleeding at 30 days, the primary outcome measure, was 10.3% in the low-dose aspirin group and 5.4% in the placebo group; the upper limit of the 95% CI of the difference exceeded the 10% noninferiority threshold set a priori (difference, 4.9 percentage points [95% CI, −3.6 to 13.4 percentage points]). This rejected the hypothesis that continued low-dose aspirin therapy was not inferior to placebo use. However, patients who received low-dose aspirin had lower all-cause 30-day mortality rates than those who received placebo (1.3% vs. 12.9%; difference, 11.6 percentage points [CI, 3.7 to 19.5 percentage points]). The low-dose aspirin group also had a lower mortality rate attributable to cardiovascular, cerebrovascular, or gastrointestinal complications (1.3% vs. 10.3%; difference, 9.0 percentage points [CI, 1.7 to 16.3 percentage points]). Kaplan–Meier estimates yielded hazard ratios of 1.9 (CI, 0.6 to 6.0) for 30-day recurrent bleeding, 0.2 (CI, 0.05 to 0.90) for mortality at 30 days, and 0.2 (CI, 0.05 to 0.70) for mortality attributable to complications.