Behçet’s disease (BD) is a systemic inflammatory disease of unknown origin that affects various parts of the body. In some patients, the prognosis of the disease appears to be altered by the involvement of the intestine (intestinal BD). In intestinal BD, deep ulcers develop in the gastrointestinal tract, typically in the ileocaecum. Intestinal lesions in patients with BD are much more common in countries in the Far East, especially Japan. The tissue damage occurring in patients with BD is believed to be caused by oxygen radicals, which are promoted by proinflammatory cytokines and arachidonic acid metabolites. New formulations of mesalazine (5-aminosalicylic acid; 5-ASA) are now available for the treatment of intestinal BD. Mesalazine breaks the chain reaction of free radical production. Mesalazine may provide an effective treatment for the promotion of long term healing of mucosal ulceration of the intestine in patients with BD.