The aim of this study was to characterize the biological activities of traditionally used medicinal plants generally collected from Kirklareli, Turkey against cancer. We evaluated the cytotoxic activities of different extracts prepared from Urtica dioica L. 1, Achillea millefolium L. ssp. pannonica 2, Malva sylvestris L. 3, Stachys cretica L. ssp. mersinaea (Boiss.) Rechf.f. (endemic) 4, Melissa officinalis L. 5, Cotinus coggyria Scop. 6, Sorbus aucuparia L. 7, and Plantago major L. ssp. major 8 species. Ethanol (a), petroleum ether (b), dichloromethane (c) and ethyl acetate (d) fractions of each plant material were obtained. Cytotoxicity in HeLa cells was evaluated using the MTT assay. Among the extracts, 7c, 2b, 6d, 7d, 7a, 2c, and 3b showed potent cytotoxic activity with IC50 values of less than 50 mu g/mL, in descending order. Dichloromethane extract of S. aucuparia is considered highly active, with IC50 of 15 03 (mean +/- SD) mu g/mL. The extracts 8a and 8b also showed good cytotoxic activity. According to the results, dichloromethane extracts of S. aucuparia had the most potent anticancer activity in HeLa cells and should be considered as a potential clinical agent. The results support the ethnomedical claims for these species and suggest further in vitro and/or in vivo studies of the active extracts.