In the recent four years, 8 cases of gastrointestinal angiodysplasia (a.d.) were observed by the authors. Analysing the conclusions drawn from the patients course of disease, they found a.d. to be the cause of an unknown gastrointestinal bleeding. a.d. can be basically diagnosed by angiography. It is often associated with liver cirrhosis or arteriostenosis. The treatment of a.d. is surgical. The recurrence and repeated appearance of bleeding can be expected even after a thoroughly performed resection.