Angiography is useful in the diagnosis of active gastrointestinal bleeding if the rate is greater than 0.5 mL/min. For upper gastrointestinal bleeding, endoscopy is the preferred initial investigation and angiography is used for diagnosis only if the site of bleeding is still obscure. Angiography is the preferred method for investigation of massive lower gastrointestinal bleeding if results of sigmoidoscopy are negative. Vasopressin infusion is most useful for control of bleeding from esophageal varices, erosive gastritis and diverticular disease of the colon. Embolization with Gelfoam or clot is possible for massive hemorrhage from a single source in poor-risk patients. This is most successful for gastric or duodenal bleeding since the collateral blood supply prevents infarction. Some of the methods and complications of embolization are discussed and examples are given. Standard surgical principles should still apply in most cases.