Classification of vascular abnormalities of the gastrointestinal tract on the basis of anatomy and pathophysiology has recently been suggested. Angiodysplasia, an example of an arteriovenous lesion, may cause either acute or chronic bleeding. Diagnosis may be difficult. High-quality standard endoscopy, capsule endoscopy, and double-balloon enteroscopy are most efficacious. Therapy using argon plasma coagulation is currently preferred. Pharmacological therapy has been employed, but a final conclusion about its efficacy cannot yet be drawn. Dieulafoy lesion, an arterial type of vascular abnormality, is rare but serious. It can be responsible for severe haemorrhage. Mechanical endoscopic methods are the most efficacious. Gastric antral vascular ectasia (GAVE), a capillary lesion, can be safely biopsied; it coincides with several diseases (including liver cirrhosis), may cause chronic iron-deficiency anaemia, and is best treated by argon plasma coagulation. Haemangiomas, benign neoplastic lesions, usually occur as part of other specific syndromes; they are difficult to manage due to the multiplicity and size of the lesions.