This paper reviews randomised trials in which the effects of histamine2-receptor antagonists have been studied in gastroduodenal ulcer haemorrhage. There is a trend in these studies that histamine2-receptor antagonists may reduce the number of rebleedings, especially in elderly patients with gastric ulcers. A randomised trial comparing cimetidine and ranitidine in high risk patients with massive gastroduodenal haemorrhage is also presented. The total mortality in this study was 12%, 15% for gastric ulcer patients and 11% for duodenal ulcer patients. There was no difference in mortality, amount of blood transfusion required, rebleedings or need for emergency surgery between the two treatment models.