OBJECTIVES: This study evaluated the changes in behaviors and the endocrine system in rat offspring at postnatal day 20 following prenatal exposure to bisphenol A (BPA), a major environmental endocrine disruptor. DESIGN: Using A predator odor (2,4,5-trimethylthiazoline [TMT]) as a stressor, I evaluate behavioral and endocrine responses to check whether the normal stress response is affected by BPA. MATERIALS AND METHODS: A low-dose group (BPA-L; 0.015 mg/kg/day) and a high-dose group (BPA-H; 1.5 mg/kg/day) were compared to assess dose dependency. The control group was not exposed to BPA. Spontaneous behaviors (rearing, ambulation, grooming, and freezing) were assessed in the presence or absence of TMT odor. RESULTS: In the control group, TMT odor increased freezing but not grooming behaviors. Conversely, in the BPA-H group, freezing was unchanged, but grooming behavior increased; however, increased freezing and grooming behaviors were observed following TMT odor exposure in the BPA-L group. In addition, blood corticosterone levels increased following TMT odor exposure in all three groups, but there was no difference between the BPA-exposure groups and the control group. Therefore, in the BPA-H group, despite the activation of the hypothalamus-pituitary-adrenal axis by TMT, freezing behavior did not increase, suggesting the absence of defensive behaviors. CONCLUSION: These findings suggest that prenatal exposure to high-dose BPA causes habituation to stress induced by the predator odor and alters the normal stress response in young rat offspring.