Abstract: Rheumatoid arthritis (RA) is an inflammatory condition, the etiology of which is not well understood. Recent reports indicate a major role of granulocytes in the pathogenesis of RA; arthritic joints are infiltrated with phagocytic leukocytes, granulocytes, and monocytes/ macrophages, and it is believed that these cells, by releasing degradative proteinases, cytokines, and reactive oxygen species, contribute to joint destruction. Hence, the apheresis of granulocytes and monocytes may benefit patients with RA. Granulocyte and monocyte apheresis was carried out in 143 patients with RA using an apheresis column (G-l) packed with 220 g cellulose acetate beads, which selectively adsorb granulocytes and monocytes. Patients received 1 or 2 apheresis sessions, each of 1 h duration per week over a 4 week period at a flow rate of 30 ml/min. Apheresis significantly reduced swollen and tender joint counts and the duration of morning stiffness, and it increased grip strength, together with suppression of tumor necrosis factor-a and interleukin-ip production by peripheral blood monocytes. It is concluded that this alternative treatment induces a kind of immunomodulation.