This study was conducted to evaluate the pharmacologic effects of Polygonum lapathifolium L. (Polygonaceae), growing naturally in Turkey. The antiinflammatory activity of the ethanol extract of the root and rhizome of P. lapathifolium was evaluated using carrageenan-induced paw edema in rats. Intraperitoneal pretreatment with extract at doses ranging from 100 to 500 mg/kg significantly inhibited the acute phase of this experimental model of the inflammatory process in a dose-dependent manner. At maximal dose (500 mg/kg), it exhibited a significantly higher action when compared with those of other doses and was found to be 1.08 times as active as indomethacin. The extract also exhibited antipyretic activity in rats with hyperthermia after SC injection of brewer's yeast. The extract, in doses of 100-500 mg/kg, possesses a pronounced effect comparable to those of the classical antipyretic drug, paracetamol. The antipyretic effects of the extract at high dose levels (1000-4000 mg/kg) were associated with obvious signs of toxicity. Doses of 100 and 500 mg/kg did not decrease the body temperature of normothermic animals (without hyperthermic stimulus). These results demonstrated that the extract of P. lapathifolium has antiinflammatory and antipyretic activity.