Human and animal investigations since the mid-1970s have demonstrated the effectiveness of cyclosporine (CsA) as an immunosuppressive agent. In the area of transplantation immunity, it has been shown to enhance success of renal, bone marrow, and liver transplantation. Moreover, certain models of autoimmune disease have been effectively treated with CsA, and a number of studies have reported encouraging results with CsA therapy for ocular inflammatory disorders, notably Behçet's disease. The most serious side effects of CsA are nephrotoxicity and hypertension; thus, conservative dosages of the drug and careful monitoring of renal function during treatment are recommended. The purpose of this review is to provide clinicians and researchers with a clear perspective of both the potential benefits and shortcomings of this agent.