The object of the invention consists of pharmaceutical formulations containing rifaximin in the shape of microgranules made gastroresistant by an insoluble polymer at pH values between 1.5 and 4.0 and soluble at pH values between 5:0 and 7.5, by their preparation and by their use in the manufacture of medicinal preparations useful in the treatment of inflammatory bowel diseases (IBD) and mainly Crohn's disease.