Objective To study the expression of Bin1b in primary cultured epididymal epithelial cells treated with different steroid hormones at various concentrations. Methods Expression of Bin1b mRNA was examined by agarose gel electrophoresis and PCR in primary cultured epididymal epithelial cells, which were treated with dihydrotestosterone (DHT, 10^-9,10^-8 and 10^-7mol/L), estradiol (E₂, 10^-9 and 10^-8mol/L)) or dexamethasone (Dex, 10^-8 and 10^-7mol/L) at different concentrations. Results The expression of Bin1b mRNA in primary cultured epididymal epithelial cells was decreased in a time-dependent manner. The mRNA level of Bin1b was decreased by 40% at day 2 and 70% at day 3; and it was hardly detectable at day 5. DHT up-regulated the expression of Bin1b mRNA in a dosage-dependent manner compared with corresponding vehicle control. 10^-9mol/L DHT up-regulated Bin1b mRNA level by 37% compared with corresponding vehicle control(P<0.05), and it was further up-regulated after the treatment with 10^-8mol/L and 10^-7mol/L DHT. E₂ and Dex at various concentrations showed no significant effects on the expression of Bin1b mRNA in primary cultured epididymal epithelial cells. Conclusion Dihydrotestosterone can up-regulate the expression of Bin1b mRNA in primary cultured epididymal epithelial cells, while estradio and dexamethasone can not.