The presented study investigates and compares the estrogenic and androgenic activities of commonly used diesters of phthalic acid (phthalates) using the XenoScreen YES/YAS assay. Phthalates are commonly used plasticizers in polymers dedicated for i.e. food and drug containers. Since phthalates are not chemically bonded to the polymer, they can leach or migrate from the polymer. Therefore, phthalates are identified as contaminants in a variety of consumer products. Investigation of estrogenic and androgenic activities of phthalates (DEP, DBP, BBP, DEHP and DINP) showed no significant effect of tested substances either on hERα or hAR receptors. Phthalates exhibited strong anti-estrogenic (IC50 for BBP=8.66μM, IC50 for DEHP=3.61μM and IC50 for DINP=0.065μM) and anti-androgenic (IC50 for BBP=5.30μM, IC50 for DEHP=2.87μM and IC50 for DINP=0.068μM) activities.