Saururus chinensis (Lour.) Baill. (Saururaceae) has been used in Korean folk medicine for the treatment of edema, jaundice, beriberi, turbid urine, carbuncle, furuncle, and gonorrhea. The components of this plant were extracted into four fractions. Of the four fractions, hexane fraction and ethylacetate fraction were highly toxic to 3T3 mouse embryo fibroblast and Raw 264.7 mosue macrophage, but n-butanol fraction and residue fractions did not show any toxic effect to those cell lines. n-Butanol fraction and residue fraction exhibited antioxidant effects on hydrogen peroxide, hydroxyl radical, and superoxide anion directly and in the 3T3 cells. All four fractions inhibited lipid peroxidation assayed by TBARS formation, and only n-butanol fraction showed protective effect on DNA breakage. n-Butanol fraction and residue fraction also showed inhibitory effects on LPS-induced nitric oxide production in Raw 264.7 mouse macrophage. Both fractions also down-regulated iNOS mRNA transcription at 6 hr after LPS stimulation. n-Butanol fraction but not residue fraction inhibited IKBa degradation at 90 min after LPS stimulation. This inhibition of IKBa degradation by n-butanol fraction explains the blocking of NF-KB activation and furthermore iNOS rnRNA transcription by this fraction. The mechanisms involved in antioxidant and anti-inflammatory effects of Saururus chinensis extracts are going to be studied further. From the results, it is believed that this plant can be a good candidate for medical drugs for its antioxidant and/or anti-inflammatory constituents.