Polybrominated diphenyl ethers (PBDE) are a class of brominated flame retardants that are recognized as global environmental contaminants with potential adverse effects on human health. This study examined the effects of prenatal exposure to PBDE on reproductive organs, neuronal development, and levels of thyroid hormones. Pregnant rats were exposed to the vehicle or deca-bromodiphenyl ether (BDE) (BDE-209; 5, 40, or 320 mg/kg body weight/d) during gestation days (GD) 6-18. There was a significant decrease in body weight gain in F1 male offspring exposed to high-dose (320 mg/kg) BDE-209. Significant increases in thyroid weight and a decrease in adrenal weight were observed in high-dose BDE-209. Thyroxine (T4) concentrations were significantly lower in F1 female offspring exposed to BDE-209 at postnatal day (PND) 42. This reduction was more pronounced in the group exposed to higher doses. A low dose (5 mg/kg) of BDE-209 significantly reduced serum estradiol concentration in female offspring but did not affect testosterone levels in males. There was no significant effect on hippocampal neurogenesis in BDE-209 treatment groups. In conclusion, there was no apparent association between thyroid hormone concentrations and low birth weight in F1 rats after gestational exposure to BDE-209.