Abstract: Fistulas, occurring in about 20 to 40% of Crohn’s disease patients, are usually resistant to conventional therapy of CD. Biologic therapies, which have revolutionary beneficial effects on diseases with an immunologic background, are a new horizon in treating fistulizing CD. The aim of this study was to evaluate the efficacy of biologic agents used to treat fistulizing CD after a brief overview on epidemiology and pathophysiology of fistulizing CD and definition of biologic therapy. Also it focuses on the trials and adverse effects of the biologic agents proved to be effective (Infliximab and CDP571).