A prospective randomized trial involving 64 patients with bleeding peptic ulcers was performed to assess the efficacy of two modalities of injection therapy. The inclusion criterion was the presence of active bleeding or a visible vessel at emergency endoscopy. Thirty-two patients were treated with epinephrine (Group A) and 32 with epinephrine plus thrombin (Group B). Permanent hemostasis was achieved in 81.3% Group A, and 84.4% Group B patients, and therapy failures occurred in 18.6% and 15.6%, respectively. Mortality was nil in both groups. There were no differences in the requirement for emergency surgery, or in the number of transfusions in the two groups. A second elective endoscopy was performed in 49 patients between the 3rd and the 5th day after admission, proceeding to a second injection therapy if a visible vessel was still seen. There were no failures among re-injected patients. With one exception, none of the failures occurred in patients in whom a second endoscopy was done. Our results suggest that injection therapy, which is a simple technique, should be considered as the initial treatment of choice in bleeding peptic ulcer. The addition of thrombin to epinephrine does not improve the results of the method. An early second endoscopy and local therapy if a visible vessel is still present, may further improve the results.