A prospective randomized trial was performed to compare the efficacy of endoscopic epinephrine injection and heat probe treatment in actively bleeding peptic ulcers. Emergency endoscopy in 1758 patients over an 18-month period identified 132 patients with active ulcer bleeding. They were randomized to receive either endoscopic epinephrine injection or heat probe treatment. After endoscopy, the patients were transferred to the surgical gastroenterology ward and were managed by surgeons unaware of the treatment option. Bleeding was initially controlled in 96% by epinephrine injection and in 83% by heat probe (P less than 0.05). There was no significant difference in outcome as measured by transfusion requirement (4.5 units vs. 3.8 units), emergency surgery (20% vs. 22%), hospital stay (8 days vs. 7 days), and mortality (2 vs. 4) between the injection group and the heat probe group. Two patients in the heat probe group experienced perforation. We conclude that both endoscopic epinephrine injection and heat probe treatment are effective in stopping bleeding from actively bleeding ulcers. Epinephrine injection is technically easier to perform and has a higher initial success rate.