Polygonum L. genus (Polygonaceae) is represented in Argentina by 21 species and some of them have been used in the traditional medicine of our country to treat affections related with fungal infections, such as skin ailments and vaginal diseases. With the aim of contributing to the correct ethnopharmacological use of this genus, in the present work we describe the antifungal properties of P. persicaria (species not studied up to now) and the bio-guided isolation of the main active compounds. Results showed that dichloromethane extracts was the most active with MICs (Minimun Inhibitory Concentrations) between 31.2 - 1000 microg/mL, validating the ethnopharmacological use of P. persicaria to treat affections related with fungal infections in the Argentinean traditional medicine.