In the diagnosis of acute gastrointestinal bleeding, endoscopy holds the first place today. Radiological investigations are indispensable whenever endoscopy cannot precisely localise the bleeding site, whenever a tumour is present or suspected, in all cases of lower gastrointestinal bleeding, and in haemobilia. A tailored radiological approach is recommended. The radiological basis programme should be at least a complete abdominal ultrasound study and plain abdominal radiograms. CT and ERCP scans may become necessary in selected cases. As a rule, angiographical localisation of the bleeding site will be successful only in the acute stage; selective visceral arteriograms have to be obtained, which may be executed in the digital subtraction technique in patients who are cooperating and clinically stable. Angiodysplasias and aneurysms, however, may be demonstrated angiographically in the interval as well. Upper and/or lower G.I. tract studies with barium or water-soluble contrast media may be indicated in the interval in order to demonstrate tumours, metastatic lesions, diverticula and gut malformations.