Rhizoma Cimicifugae (RC) has been used traditionally to treat pain and inflammation in Korea. The present study was conducted to gain insights into the mechanism of action regarding analgesic and antiinflammatory activities of RC extracts. RC was first extracted with methanol. The methanol extract (A) was fractionated to an ether-soluble fraction (B) and a water-soluble fraction (C). Fraction C was fractionated to a butanol-soluble fraction (D) and a water-soluble fraction (E). Each fraction (100 mg/kg, i.p.) was tested for analgesic and antiinflammatory activities. Administration of fractions A and D caused dramatic analgesic effects based on acetic acid writhing and tail-flick assays. However, fraction E had an analgesic effect only based on the acetic acid writhing assay. Fractions A, D and E exerted antiinflammatory effects on the rat paw oedema assay. The fractions A, D, E had an inhibitory action on the bradykinin/histamine-mediated contractions of guinea-pig ileum. In addition, fractions A, D and E had the ability to inhibit the production of LPS-induced 6-keto-PGF1alpha production in macrophage cultures. Taken together, these results provide scientific evidence that RC extracts exert analgesic and antiinflammatory effects by inhibiting bradykinin/histamine mediated actions and inhibiting 6-keto-PGF1alpha induction.