Sixteen Crohn's disease patients with active fistula who had failed standard medical therapy were treated with intravenous cyclosporine. Ten patients had perirectal disease, four had enterocutaneous fistula, and two had rectovaginal fistula. Patients were initially treated with intravenous cyclosporine, 4 mg/kg/day, and then switched to oral cyclosporine, 6-8 mg/kg/day. Improvement was graded using the Present-Korelitz criteria, and success was defined as moderate to total closure of the fistula. Fourteen of 16 patients (88%) responded in the acute phase to parenteral cyclosporine. Closure of fistula occurred in seven (44%) with moderate improvement in the remaining seven (44%). Subsequently, five patients (36%) relapsed to some degree on oral cyclosporine (three severe and two mild relapses). Nine (64%) patients maintained their improvement in the chronic phase. Chronic steroids could be discontinued in 6/8 (75%) of patients. Mild side effects were common [paresthesias (75%) and hirsutism (19%)]. A single patient had severe paresthesias requiring discontinuation of therapy. Mild hypertension was noted in four (25%) and one patient (6%) had to be withdrawn because of nephrotoxicity, which reversed after stopping cyclosporine. We conclude that intravenous cyclosporine is effective therapy for perianal, rectovaginal, and enterocutaneous fistula in Crohn's disease. Its future role awaits controlled trials as well as determination of the risk-benefit ratio.