We examined whether orally administered bisphenol A transfers from the maternal rat to the fetus. After oral dose of 10mg/kg bisphenol A, it immediately appeared in maternal blood, and transferred into the fetuses. The concentration of bisphenol A in both maternal blood plasma and fetuses peaked within 1h after administration. The values were approximately 34 ppb and 11ppb, respectively. At 3h, the concentration of bisphenol A in maternal blood plasma had decreased to approximately 10% of the peak value. The 3-h decrease in fetuses was only about 40% of the peak, and by 24h, the fetal concentration had increased again to the nearly 70% of the peak value. The results suggest that bisphenol A might easily pass through the placental barrier, unlike sex hormones such as estrogen.