The present study was carried out to examine the effects of Kami-hwal-hyeol-tang(KHHT) on the immune responses of synoviocyte cells prepared from the rheumatoid arthritis patients, and also on the collagen-mediated arthritis in mouse model. Several experiments were performed in vitro and in vivo to analyse the immunomodulatory effects of KHHT, and the major findings are summarized below: 1. KHHT did not show the cytotoxicity against mLFCs and hFLSs. 2. KHHT inhibited gene expression of IL-1β, IL-6, TNF-α, COX-2, NOS and GM-CSF in hFLSs. Furthermore, KHHT-treated hFLSs showed reduced production of pro-inflammatory cytokines such as IL-1β and IL-6 compared to the control cells. 3. KHHT treatment of hFLSs inhibited the binding activity of NF-kB and AP-1 to their consensus DNA sequences. 4. KHHT treatment(400 ㎍/㎖) of hFLSs significantly inhibited hFLSs proliferations compared to the control cells. 5. KHHT significantly reduced the production of ROS in hFLSs compared to the control cells. The present data show that KHHT plays an important role for the regulation of AP-1 and NF-kB gene expression. Also, it was found that KHHT has anti-arthritis effect. Further studies of KHHT in relation to RA therapeutics may provide important information to develop drugs to treat this disease.