Numerous uncontrolled studies and one controlled trial of cyclosporine therapy suggest that this selective inhibitor of cell-mediated immunity may be of benefit in patients with chronically active Crohn's disease. In addition, uncontrolled studies indicate that cyclosporine may be useful in the following settings: fistulous Crohn's disease; corticosteroid sparing in Crohn's disease; severe ulcerative colitis; and refractory proctosigmoiditis. The major advantages of cyclosporine therapy are apparent efficacy in patients with refractory disease and a rapid onset of response. Nevertheless, the incidence of relapse is high after cyclosporine therapy is discontinued, and this outcome is not prevented by low-dose maintenance therapy. Furthermore, the frequency of occurrence of cyclosporine-related side effects during treatment of patients with inflammatory bowel disease is high; paresthesias and hypertrichosis are the two most common adverse effects reported in the literature. Although the potential for permanent renal damage is of concern, serious, irreversible toxicity seldom occurs. Ongoing clinical trials will provide additional information about the efficacy and safety of cyclosporine for the aforementioned indications.