Equisetum hyemale L. has been prescribed widely as a traditional medicine for the treatment of inflammatory diseases such as rheumatoid arthritis, conjunctivitis, pyelonephritis. In order to identification the mechanism, we examined an antioxidant and anti-inflammatory activity of 85% methanol extract of E. hyemale. In this study E. hyemale exhibited strong scavenging effect on 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical, superoxide radical, and nitric oxide. To elucidate the anti-inflammatory properties of E. hyemale, we investigated the inhibition effects of nitric oxide and IL-6 by E. hyemale in IFN-gamma and LPS-stimulated mouse peritoneal macrophages. E. hyemale suppressed nitric oxide, IL-6 production and iNOS expression dose-dependently without notable cytotoxic activity. These data suggest that E. hyemale might be useful in inflammatory diseases by inhibiting the free radicals and inflammatory mediators.