The rise of fistulae in Crohn's disease has been classed with the disorder complications, although it is a possible component of natural development of the so-called A type (De Dombal classification) or aggressive-perforating type (Greenstein's classification) of this idiopathic intestinal inflammation. Fistulae are accompanying colic localization of Crohn's disease in 20%, ileocolic affection in 40%, where 35% of them are perianal fistulae, and about 34% entero-enteral or entero-cutaneous ones. Other complications (urogenital tract, biliary tract) are mentioned infrequently in literature. Besides surgical approaches in the therapy, dominant post in the conservative area is taken up by an antitumor necrotizing factor, antibiotics and immunosuppressives whose position is, however, the most problematic although the literature references about the effectiveness of azathioprine, 6-mercaptopurine, cyclosporine, tacrolime and methotrexate have had nearly 25-years tradition. The authors present their own experience with applying a combination of cyclosporine, azathioprine in the treatment of perianal fistulae in a set of 21 patients from the period of 1995-2000. In their opinion, the therapy success is limited especially by early starting the treatment (11 cases of effective therapy) and choosing a resolute method that is, according to them, sequential immunosuppression. (Tab. 2, Ref. 32.)