Gastrointestinal involvement represents only 14% of the anatomical sites of Behçet's syndrome in France. The various segments of the gastrointestinal tract may be affected. Episodes of mucosal aphthae are more frequent in the oesophagus than in the stomach or duodenum. Intestinal involvement constitutes the major gastrointestinal localisation. Colonic or ileo-colonic lesions may appear after several years of recurrent aphthosis and present in the form of acute complications (perforation, massive haemorrhage) or by prolonged haemorrhagic diarrhoea with marked deterioration in the general state. The radiological and endoscopic signs are similar to those observed in various forms of severe acute colitis such as haemorrhagic proctocolitis or Crohn's disease. The diagnosis of an intestinal localisation of Behçet's syndrome is based on the richness of the extra-intestinal signs and moreover on the presence of deep colonic ulcerations frequently situated in healthy mucosa, the presence of an adjacent non-specific inflammatory infiltrate affecting all of the colonic wall, lesions of vasculitis and perivasculitis with signs of leukocytoclasis and fibrinoid necrosis. Surgical treatment is frequently necessary. The high incidence of ulcerative recurrences in the anastomoses, in which fistulae may also develop, requires extensive intestinal resections or diversions by long-term ileostomies.