PURPOSE: In this study, a possible suppressive effect of a flavon extracted from Artemisia absinthium on a mouse collagen-induced arthritis (CIA) model was investigated.0aMETHODS: DBA/1 mice were injected intradermally with emulsified chicken type II collagen. Three weeks after immunization, a flavon was introduced p.o. everyday. Clinical incidences of arthritis and arthritis index were measured. Measurement of anti-collagen antibodies and a stimulation index of the splenocytes of the mice were measured. IL-10 and TNF-alpha in the supernatants of the mice sera were measured by ELISA. mRNA expression for IL-10 and TNF-alpha in the splenocytes were tested.0aRESULTS: Flavon extracted from Artemisia absinthium appears to be an effective suppressor of CIA in mice. The serum anti-collagen antibody level and stimulation index of the cultured splenocytes showed no significant differences among the three experimental groups. Also serum IL-10 and TNF-alpha levels did not show any significant differences among the three experimental groups. An increased expression of mRNA for IL-10 was observed in the splenocytes treated with flavon.0aCONCLUSION: With these results, flavon extracted from Artemisia absinthium appears to have a suppressive effect of CIA. The mechanism of the suppressive effect of flavon extracted from Artemisia absinthium may be from a stimulation of IL-10 production.