Filtration Leukocytapheresis(LCAP) is an alternative to thoracic duct drainage and LCAP using a centrifuge method with the advantages that it can be performed easily and inexpensively. Clinical trials revealed that LCAP is a safe and effective therapy for patients with drug-resistant rheumatoid arthritis(RA). Assessment of RA before and after LCAP showed a substantial and rapid improvement in tender joints counts, swollen joint counts, and patient's and physician's assessments. Careful analysis indicated that 64-80% of patients with RA showed > or = 20% improvement following LCAP therapy. Furthermore, we investigated the clinical evaluation of LCAP for RA over the 3 year-study period. Possible therapeutic mechanisms of LCAP on RA are summarized.