The study investigated the responsiveness of a recombinant Saccharomyces cerevisiae yeast strain to screen estrogen-like chemicals in order to use it as a first level short-term bioassay for environmental preventive medicine purposes. We used the yeast strain RMY326 ER-ERE, containing the human estrogen receptor alpha and a reporter gene lacZ encoding the enzyme b-galactosidase. We tested the natural steroid hormone 17beta-estradiol, diethylstilbestrol, colchicine, some phytoestrogens and pesticides, and organochlorine insecticides. The relative inductive efficiency (RIE) and EC50 values confirmed the sensitivity and specificity of the yeast strain. A statistically significant reproducibility of results in repeated experiments was assessed.