Acaena splendens H. et A., Rosaceae, has been used in Chilean traditional medicine for the treatment of fever and inflammation. The antipyretic and antiinflammatory properties of the infusion, methanol, petroleum ether and dichloromethane extracts of the whole plant were examined. A description and results of the in vivo studies are presented, based on the reduction of bacterial pyrogen-induced fever in rabbits and carrageenan-induced paw edema in guinea pigs, as well as acute toxicity assays of the methanol extracts in mice. The acqueous, methanol and dichloromethane extracts showed marked antipyretic and antiinflammatory activities; the dichloromethane extract being the most active in both assays. The petroleum ether was subjected to bioassay-guided fractionation by column chromatography, yielding an active fraction containing a mixture of triterpenes in which β-amyrin was identified as a major component and lupeol was also present. Similarly, the dichloromethane extract yielded olea