We describe the first report of a patient with rheumatoid arthritis (RA) who developed refractory pure red cell aplasia that was successfully treated with cyclosporin A (CyA). Since no inhibitory activity against bone marrow was observed in the whole serum, it is possible that the clinical efficacy of CyA on both RA and aplasia was explained by its effects on T cells that might be involved in the development of these diseases.