Phytoestrogen genistein can exhibit cytoprotective and antioxidant properties, providing chemopreventive action, and produce cytotoxic effects on some tu- mors. In this work, the cytotoxic, cytoprotective, and antioxidant properties of genistein have been studied on model tumor cells (human cervical cancer HeLa cells) and normal cells (rat dermal fibroblasts, RDF). For assessing the cytotoxic effect of genistein (spectrophotometric MTT assay), the reference drug was cis-diaminodichloroplatinum (cisplatin); for evaluating antioxidant action, beta-estradiol was the reference drug. It is established that genistein produces a cyto- toxic effect only at high concentrations, IC50 = 20 mM and 14 mM for RDF and HeLa cells, respectively, which is 30 and 10 times higher than IC50 for cisplatin on these cells. Genistein like estradiol, but unlike cisplatin, had no effect on the mitochondrial pore induction from rat liver mitochondria. Thus, genistein at physiological concentrations (up to 200 n) acts as a cytoprotective agent. High antioxidant activity of genistein also suggests the possibility of its use as a chemopreventive drug.