In the present study, we demonstrated for the first time that atrazine exerts an estrogen-like activity in ovarian and breast cancer cells through GPR30, which is recently of interest because of its ability to mediate rapid estrogen signals (Albanito et al. 2007, 2008; Filardo et al. 2006, 2007; Revankar et al. 2005, 2007). The gene discussed is GPER1; the disease is breast carcinoma.