Abstract: Objective To investigate the effects of 17β-estradiol on the expression of nuclear factor kappa B(NF-кB) and Toll-like receptor 4(TLR4)in lipoplysaccharide(LPS)-stimulated RAW264.7 cells. Methods The expression of TLR4 mRNA in RAW264.7 cells was detected with reverse-tanscription-PCR(RT-PCR).The activity of transcription factor NF-кB was detected with method of luciferase reporter. Results The relative expression level of TLR4 mRNA was 1.23±0.21, 1.52±0.28,and 1.11±0.27 in the control group,LPS stimulation group,and 17β-estradiol group,respectively.Meanwhile, the relative value of NF-кB activity was 126±32,306±58,and 247±37 in the control group,LPS stimulation group,and 17β-estradiol group,respectively.17β-estradiol could decrease the expression of TLR4 mRNA and the transcription activity of NF-кB in LPS-stimulated RAW264.7 cells(P<0.05). Conclusion 17β-estradiol has anti-inflammatory effect via regulation of TLR4 expression and NF-кB transcriptional activity.