A case of a 32-year-old male patient with lower gastrointestinal bleeding is reported as an initial manifestation of Behçet's disease. The early diagnosis of this chronic-systemic disease is often very difficult, in particular with regard to the differentiation from chronic inflammatory bowel diseases. In addition, lower gastrointestinal bleeding is a rare manifestation of Behçet's disease. An immunosuppressive therapy was initiated and the course of the disease with recurrent oral ulcerations gave evidence for the diagnosis. Further bleeding episodes or other gastrointestinal symptoms have not been observed during a follow-up period of 36 months. The diagnostic problems and the therapeutic management of the disease are discussed in relation to neighbouring entities.