The main goal of the present study was the evaluation of the potential estrogenic properties of the active substances of selected fungicides, boscalid, cyprodinil and iprodione, by using the following in vitro bioassays for measuring estrogenic activity: estrogen-dependent (ER+) human breast cancer cell line (MCF-7) proliferation test or E-screen test and luciferase transfected human breast cancer cell line T47D-KBluc gene-reporter assay. The gene discussed is ESR1; the disease is breast carcinoma.