Extracts from the roots of Peucedanum ostruthium (L.) Koch were investigated for their antiphlogistic and antipyretic effects as well as for their influence on arachidonic acid metabolism. On carrageenan-induced rat paw edema, oral administration of 10% ethanolic extracts led to a marked inhibition of the edema. By means of bioassay-oriented fractionation of extract, 6-(3-carboxybut-2-enyl)-7-hydroxycoumarin proved to be the most important anti-inflammatory principle of the plant. 30 micrograms/kg of this compound inhibited the formation of edema to an extent of 50%. On the perfused rabbit ear and on polymorphonuclear leukocytes the extract and the active compound have been characterized as dual inhibitors of cyclooxygenase and 5-lipoxygenase activities. Moreover, an antipyretic effect of i.p. administered extract and compound were evaluated in rats with comparable hyperthermia after s.c. injection of brewer's yeast.