The aim of present study was to investigate the anthelmintic activity of Urtica dioica L. (nettle) in Swiss albino mice naturally infected with Aspiculuris tetraptera. Methanolic extracts obtained from leaves and seeds of U dioica were evaluated for their in vivo anthelmintic activity. The 250 mu L (175 mg mL(-1)) extracts were administered orally on daily basis. Results showed that methanolic extract of U. dioica seeds possessed only a slight anthelmintic activity. In contrast, methanolic extract of leaves exhibited potent anthelmintic activity.