Aplastic anaemia developed in a 33-year-old woman whose rheumatoid arthritis was refractory to the administration of many drugs, including penicillamine and gold. Allogeneic bone marrow transplantation reversed the haematological abnormality and simultaneously resulted in a 2-year period of relief from joint pain. Symptoms then reappeared and the serological tests for rheumatoid arthritis again became positive. The arthralgia has responded slowly to the administration of anti-inflammatory drugs and steroids. The protracted asymptomatic period may have been due to the intense immunosuppression required for marrow grafting and the subsequent administration of cyclosporin. Since she developed chronic graft-versus-host disease, the arthritis may be an unusual complication of this syndrome.