Thirty-four patients with acute gastroduodenal hemorrhage were treated with intravenous Cimetidine. Preliminary endoscopy was done at the onset of bleeding to determine the source of bleeding and to rule out the presence of a brisk arterial bleeding site that would require immediate operation for control. Sixteen of the patients had primary peptic ulcer disease and 18 patients had "stress ulcer" syndrome. The bleeding stopped following Cimetidine administration in 14 of the 16 peptic ulcer patients (88%) and in 13 of 18 stress ulcer patients (72%). There was no subsequent rebleeding. The data suggest that Cimetidine is of value in the immediate nonoperative management of acute gastroduodenal hemorrhage. Further, the availability of Cimetidine for postoperative use may modify the surgical approach to stress ulcer bleeding.