Crohn's recurrence is the appearance of objective signs - defined radiologically, endoscopically or pathologically - of Crohn's disease in the bowel of a patient who has previously had a resection of all macroscopically diseased tissue. New lesions can be visualized endoscopically within weeks to months after ileal resection and ileocolonic anastomosis in the neoterminal ileum. The evolution of these lesions mimics the natural history of ileal Crohn's disease at the onset. If we are able to prevent recurrence of early lesions, we will probably interrupt the natural course of the disease. The drugs tested to date include different 5-aminosalicylate formulations, nitro-imidazole antibiotics, steroids and azathioprine. None of these therapies has convincingly been shown to prevent recurrent lesions. Metronidazole and ornidazole are effective, but cannot be used in the long-term because of side effects. Since there is a lag time of months to years between the development of recurrent lesions in the bowel and the recurrence of symptoms, we recommend performing imaging of the bowel 6 months after the operation to assess the severity of recurrence, and basing the further treatment strategy on this assessment.