A survey is given on the present state of experience with Cimetidine. Cimetidine significantly promotes healing of duodenal and gastric ulcers; this effect is especially significant in countries with low spontaneous ulcer healing. Prophylactically administered Cimetidine is the only drug capable of decisively lowering the recurrence rate of duodenal ulcers. In certain cases, Cimetidine long-term treatment therefore seems to compete with elective gastric operations. However apart from the operative risk surgery of the stomach (especially selective gastric vagotomy) still provides certain advantages. Controlled long-term trials are still required in order to come to a clear-cut delimitation between the indications for Cimetidine prophylaxis and elective operation. Furthermore prophylaxis with Cimetidine prevents gastric bleeding from erosions in stress-patients. Even in Zollinger-Ellison-syndrome Cimetidine enables ulcers to heal and patients to reach operability. In patients with operable gastrinomas the long-term treatment with Cimetidine seems to replace palliative total gastrectomy by curative resection of the tumour.