OBJECTIVE: To investigate the mechanism of the different levels of serum bisphenol A (BPA) between rat and mouse after oral administration. METHODS: A total of 18 specific pathogen free (SPF) male rats and 18 mice were treated with 300 mg/kg BPA by oral administration, blood samples were taken from rats and mice after BPA administration at 0.5, 1.0, 12.0 h time points (n = 6 at each point). Serum BPA levels were quantified using fluorescence-high performance liquid chromatography (FL-HPLC) analysis. The rats and mice (n = 6, respectively) were perfused with 100 ml of 0.1 mmol/L BPA by intestinal absorption in situ, then the BPA levels of perfusion fluid at 0.5, 1.0, 2.0 h time points and serum at 2.0 h after BPA perfusion were determined by FL-HPLC analysis. The levels of UDP-glucuronosyltransferase 2B1 (UGT2B1) mRNA expression in the liver of rats and mice were analyzed by semi-quantitative RT-PCR and UGT2B1 enzymatic activity was determined by FL-HPLC method. The rats and mice (n = 6, respectively) were treated with 300 mg/kg BPA by oral administration after fasting 24 h, the feces were collected during 24 h and the levels of BPA in feces were determined by FL-HPLC analysis. RESULTS: At 0.5, 1.0, 12.0 h after oral administration at 300 mg/kg BPA, the levels of serum BPA in mice ((66.57 ± 14.95), (51.16 ± 16.06), (22.73 ± 5.00) µg/ml, respectively) were significantly higher than in rats ((15.63 ± 5.65), (18.34 ± 5.02), (7.65 ± 2.58) µg/ml, respectively) (F values were 50.660, 17.957, 8.420, respectively, P < 0.05), the rates of absorption in mice small intestine during 0 h-, 0.5 h-, 1.0 - 2.0 h ((10.20 ± 4.20), (1.49 ± 0.67), (1.31 ± 0.55) µg × cm(-2) × min(-1), respectively) were higher than that in rats ((1.87 ± 0.69), (0.47 ± 0.13), (0.36 ± 0.08) µg × cm(-2) × min(-1), respectively) (F values were 14.954, 8.877, 11.536, respectively, P < 0.05), the serum BPA levels in mice ((22.64 ± 4.35) µg/ml) were significantly higher than in rats ((4.13 ± 0.83) µg/ml) after 2 h perfusion with 0.1 mmol/L BPA (F = 74.643, P = 0.000), the levels of UGT2B1 mRNA expression and enzymatic activity in the rats liver were obviously higher than in the mice liver. After oral administration at 300 mg/kg BPA, the feces BPA levels of rats ((1.50 ± 0.32) mg/g) were significantly higher than that of the mice ((0.57 ± 0.35) mg/g) (F = 21.215, P = 0.001) during 24 h. CONCLUSION: The serum BPA level of mouse is significantly higher than the rat after oral administration at 300 mg/kg BPA, which may be caused by BPA high absorption rate of mouse small intestine and strong ability of BPA glucuronidation and excretion of the rat.