No prior randomized controlled trial (RCT) has reported patient outcomes of large over-the-scope clip (OTSC) compared to standard hemostasis as initial endoscopic treatment of severe NVUGIB. This was our study aim. Patients with bleeding ulcers or Dieulafoy's lesions and major stigmata of hemorrhage - SRH (active spurting bleeding, visible vessel, or clot) - or lesser SRH (oozing bleeding or flat spots - with arterial blood flow by Doppler probe) were randomized to OTSC or standard endoscopic hemostasis (with hemoclips or multipolar electrocoagulation - MPEC). Patients and their healthcare providers were blinded to treatments and made all post-randomization management decisions. Ulcer patients received high dose intravenous infusions of proton pump inhibitors (PPI) for 3 days, then 27 days of oral PPI. 30 day outcomes were prospectively recorded; data management was with SAS; and data analysis was by a statistician. 53 patients (25 OTSC, 28 Standard) were randomized, with similar baseline risk factors. However, there were significant differences in OTSC vs. Standard groups in rates of rebleeding (4% vs. 28.6%; p = .017; relative risk 0.10, 95% confidence intervals 0.01, 0.91; number needed to treat 4); severe complications (0 % vs. 14.3%); and post-randomization units of red cell transfusions (0.04 vs. 0.68). All rebleeds occurred in patients with major SRH and none with lesser SRH. 1. OTSC significantly reduced rates of rebleeding, severe complications, and post-randomization red cell transfusions. 2. Patients with major stigmata benefited significantly from hemostasis with OTSC, but those with lesser stigmata did not. (ClinicalTrials.gov, Number: NCT03065465).