Antibiotics are often employed in the treatment of Crohn's disease, with interesting results. However indiscriminate suppression of intestinal bacteria may be harmful and long-term use of antibiotics is burdened by side-effects and by the risk of developing bacterial resistance. Manipulation of enteric flora with probiotic compounds would be a possible and appealing alternative. First aim of our study has been to investigate the efficacy of this probiotic in reducing the endoscopic recurrence rate or in reducing the severity of recurrent lesions at 1 year after surgery. Secondary goal has been the reduction of the clinical recurrence rate. Forty-five patients have been randomised to receive Lactobacillus rhamnosus strain GG or placebo for 12 months. The results have shown no differences in endoscopic and clinical remission between the two groups.