Several species of the Polygonum genera are collectively known in Brazil under the name "erva-de-bicho". In tradicional medicine, these species often mistaken for each other and are probably used for the same therapeutic purpose. In this study, the hydroalcoholic extract of the aerial parts of Polygonum persicaria was isolated, and the phytochemical composition was examined. In addition, the anti-inflammatory activity was tested in rats by paw edema inhibition analysis. The effects on locomotion were tested in rats, using the open field test. Flavonoids, mucilage, saponins, tannins and essential oils were detected. The extract showed anti-inflammatory and decreased locomotion after intraperitoneal administration to rats.