The root of Clematis chinensis Osbeck has been used widely in rheumatoid arthritis in Chinese traditional medicine and AR-6 is a triterpene saponin isolated from it. In this present study, we investigated in vivo effects of oral AR-6 in chronic rat adjuvant-induced arthritis (AA) and in vitro effect in macrophage and synoviocytes cells. Arthritic scores and serum inflammatory mediators were evaluated 19 days after AA induction by endermic injection of Freund's complete adjuvant in Sprague-Dawley(S-D) rats. Oral administration of AR-6 to arthritic rats resulted in a clear decrease of clinical signs compared to untreated controls. The synoviocyte and macrophage response ex vivo were then analyzed. Anti-arthritic effects of AR-6 correlated with significant decrease of NO and TNF-alpha produced by peritoneal macrophages, ex vivo and in vitro. AR-6 also significant decreased the proliferation of synoviocyte. These data indicate that AR-6 is a potential anti-inflammatory therapeutic and preventive agent.