Intestinal lesions in Behçet's syndrome are much more common in Japan than in the Western World. Colonic or ileo-colonic lesions develop after several years of recurrent aphthae and are manifested by acute complications, such as perforation or massive haemorrhage, or by protracted haemorrhagic diarrhoea with progressive deterioration of the patient's general condition. Radiological and endoscopic findings are similar to those of severe acute colitis, such as ulcerative colitis or Crohn's disease. The diagnosis of Behçet's syndrome involving the bowel rests on the presence of numerous extra-intestinal lesions and of extensive colonic ulceration often located in otherwise healthy parts of the mucosa. Histology shows, beside a non-specific inflammatory infiltrate affecting the entire wall of the colon, lesions of vasculitis and perivasculitis with images of leucocytoclasia and fibrinoid necrosis. Surgery is often necessary, requiring wide intestinal resections and long-term derivation ileostomies because of the high incidence of recurrent ulcers at the site of anastomosis, where fistulae may also develop.