Background: Recent studies indicate that persistent intestinal inflammation in patients with Crohn's disease (CD) might be caused by abnormal intestinal microbiota. This hypothesis may suggest a beneficial effect of antibiotics in CD therapy. So far, guidelines do not recommend antibiotics except in the treatment of complicated CD, and there are few studies on the effects of rifaximin in these patients. Methods: Between December 2011 and December 2012, we performed a blinded randomized trial in 168 patients with a previous history of moderately active CD concerning the efficacy of rifaximin. All the patients had previously achieved remission with standard therapy (prednisone/budesonide). Data from patients receiving 800 mg of rifaximin (83 patients) twice a day for 12 weeks were compared with those from patients who received placebo (83 patients). The primary endpoint was maintaining remission during the follow-up. Results: All the patients (100%; 83/83) on 800 mg of rifaximin were in remission after 12 weeks of treatment in comparison with 84% (70/83) of the placebo group. This significant difference was also persistent at the 24-week follow-up [78% (65/83) vs. 41% (34/83), respectively]. The last evaluation performed at 48 weeks revealed disease activity in 45% (38/83) of the patients of the rifaximin group, i.e. a significant decrease compared with the placebo group [75% (63 of 83)]. Conclusions: Remission previously obtained with standard treatment can be sustained in patients with moderately active CD after the administration of 800 mg of rifaximin.