The aim of the conducted studies was to check the activity of active substances of selected fungicides: boscalid, cyprodinil and iprodione and to analyze their potential estrogenic activity. The studies were carried out using two model cell lines MCF-7 and T47D- KBluc. The cells were selected for their response to 17ß-estradiol, which meant that they could be used to study estrogenic or antiestrogenic activity of chemical substances. The cytotoxic activity of the fungicides tested was assessed using the MTT test on two cell lines. The estrogen receptor (ER) reporter gene test was performed, which is referred to as the T47D-KBluc test. The E-Screen test was performed on the MCF-7 line, the principle of which is based on the increased proliferation of human breast cancer cells in the presence of substances with potential estrogenic activity. ROS content and zeta potential were also estimated.