Probiotics are living micro-organisms that belong to the normal enteric flora and exert a beneficial effect on health and well-being. The rationale for the therapeutic use of probiotics in pouchitis (the most frequent long-term complication following pouch surgery for ulcerative colitis) and postoperative recurrence in Crohn's disease is based on convincing evidence suggesting a crucial role for the endogenous intestinal microflora in the pathogenesis of these conditions. Positive results have been obtained with the administration of highly concentrated probiotic preparations in preventing the onset and relapses of pouchitis. Further controlled studies are needed to establish the efficacy of probiotics in the prophylaxis of postoperative recurrences of Crohn's disease and in the treatment of mild pouchitis.