The total ethanol extract of Angelica koreana radix (UmbeUiferae) showed potent inhibitory effect on tumor necrosis factors (TNF-${alpha}$) production from LPS-stimulated RAW 264.7 cells in screening studies on 118 Korean medicinal plants. The activity-guided fractionation of the total ethanol extract resulted in the isolation of 4 compounds, including active substances. The chemical structures of the compounds isolated were established by chemical and spectrometric analyses as imperatorin, isoimperatorin, osthol and oxypeucedanin. Among them, osthol, oxypeucedariin and isoimperatorin showed significant inhibitory activities on TNF-${alpha}$ production as 54.3${pm}$2.1%, 33.6${pm}$1.0% and 17.7${pm}$3.0%, respectively, at 12.5${mu}$g/ml.