Patients with Crohn's disease are at risk for developing both internal and external fistulae. These can be asymptomatic incidental radiologic findings or causes of incontinence, chronic pain, abscesses, and sepsis. They can have a devastating impact on quality of life. Careful prospective studies of therapy are few in adult medicine and entirely lacking in the pediatric age group. Assessment and management require a coordinated effort between gastroenterologist, radiologist, and surgeon. Principles of management include surgical drainage of infection combined with medical therapy. Only infliximab has been studied in prospective, double-blinded fashion and clearly shown to be of use in the short term. There is good evidence that metronidazole may be useful acutely and that 6-mercaptopurine azathioprine may help to maintain closure. Diverting ostomies are of very limited value and corticosteroids seem to make matters worse. There are many other therapies that have been reported to be helpful in small, uncontrolled studies.