We report a patient who developed recurrent acute inflammatory demyelinating polyradiculitis (AIDP) receiving immunosuppressive treatment with cyclosporin and prednisone for secondary chronic graft versus host disease (GVHD) following allogeneic bone marrow transplantation (BMT) from an unrelated donor for chronic myelogenous leukemia (CML). After the second relapse of AIDP, cyclosporin was discontinued and a rapid, sustained improvement of his neurological deficits occurred. The role of cyclosporin and systemic CMV infection in the pathogenesis of AIDP in this patient are discussed.