For 4 decades, stigmata of recent hemorrhages in patients with non-variceal lesions have been used for risk stratification and endoscopic hemostasis. The arterial blood flow that underlies the stigmata is rarely monitored, but can be used to determine risk for rebleeding. We performed a randomized controlled trial to determine whether Doppler endoscopic probe monitoring of blood flow improves risk stratification and outcomes in patients with severe non-variceal upper gastrointestinal hemorrhage.