A growing body of laboratory and clinical evidence suggests that the cytopenia of MDS is at least partly a result of cytotoxic T cell activity. Treatments to abrogate T cell activity such as anti-thymocyte globulin alone and cyclosporine alone have demonstrated varying degrees of success in alleviating the cytopenia of MDS. A response to such therapy in MDS is associated with improved survival. Experience with aplastic anemia suggests that the combination of these two agents should be more effective in suppressing cytotoxic T cell activity and alleviating cytopenia. This protocol proposes using the combination of antithymocyte globulin (ATG) and cyclosporine (CSA) to treat the cytopenia of MDS, in an effort to improve the response rate to immunosuppressive therapy in this disease.