Postoperative recurrence of Crohn's disease is very common and almost invariably appears at the ileal side of the ileocolonic anastomosis. Luminal factors are believed to play an essential role in triggering the earliest inflammatory events. The characteristics of recurrent disease are often very similar to those of the original presentation before surgery. Several 5-ASA preparations as well as antibiotics such as metronidazole have been shown to affect incidence and/or severity of recurrence of Crohn's disease.