Twenty-eight consecutive HLA matched patients undergoing allogeneic bone marrow transplantation received prophylaxis for acute graft-versus-host disease with combined cyclosporine and methylprednisolone. The incidence of grades II-IV acute GVHD was 28.5%, a figure similar to that reported for two other drug regimens. The incidence of chronic GVHD in patients surviving longer than 150 days was 73%. Toxicity, especially renal, was acceptable and a number of potential problems associated with the use of methotrexate were avoided. While this regimen and similar ones have reduced the incidence and severity of acute GVHD the problem remains formidable and newer approaches are clearly needed.