Genistein is a product of naturally occurring isoflavones at relatively high levels in soybeans. The harmful effects of ethanol are attributed to the induction of biological processes which lead to an increase in the generation of reactive oxygen species in fetuses. In this study, we investigated the effects of genistein ($1{ imes}10^{-8}$ and $1{ imes}10^{-7};{mu}g$/ml) on gene expressions of the representative cellular antioxidative enzymes in ethanol (1 ${mu}l$/ml)-treated mouse fetuses during the critical period (embryonic days 8.5~10.5) of organogenesis using a semi-quantitative RT-PCR analysis. The mRNA levels of cytosolic glutathione peroxidase (GPx), phospholipid hydroperoxide GPx, cytosolic CU,Zn-superoxide dismutase (SOD), and mitochondrial SOD were significantly decreased in ethanol-treated fetuses. However, the mRNA levels of ethanol plus genistein-treated fetuses were significantly higher than those of ethanol alone fetuses. These results indicate that genistein can up-regulate the expressions of GPx and SOD mRNAs reduced by the ethanol treatment in fetuses.