Internal fistulas occur in 5-10% of patients with Crohn's disease. The clinical presentation of each of the three main types of internal fistulas--enteroenteric, enterovaginal, and enterovesical fistulas--is important in determining the best management. Asymptomatic fistulas usually require no treatment, but fistulas that cause severe or persistent symptoms necessitate intervention. Previously regarded as a surgical condition requiring resection, some internal fistulas are amenable to a more conservative approach involving medical therapy, surgical repair, or both. So far, there have not been any prospective studies designed specifically to assess the efficacy of a medical treatment of internal fistulas, and information about treatment results is gleaned from trials in which patients with internal fistulas have been included and from retrospective reports. Drugs that have been reported to close internal fistulas partially or completely include azathioprine, 6-mercaptopurine, mycophenolate mofetil, cyclosporine A, tacrolimus, and infliximab. Reparative surgical techniques include transrectal and transvaginal mucosal advancement flaps, cutaneous advancement flap, and anal stricturectomy in combination with a rectal mucosal advancement sleeve. Prospective trials of medical therapy and combination medical and surgical therapy for internal fistulas are needed to provide evidence to support the use of these new therapeutic approaches.