Aim To investigate whether hypoxia could induce the expression of ABCA1 and cholesterol efflux in RAW264.7 cells. Methods RAW264.7 cells were cultured under hypoxia condition(37℃,5%CO2,1%O2)and normoxia conditon(37℃,5%CO2,20%O2) for 0,6,12,24 or 48 hours respectively,and ABCA1 mRNA and protein expression was detected by real-time PCR and Western blot,respectively.Using ox-LDL 3H-cholesterol,ApoA-I-mediated cholesterol efflux in RAW264.7 cells under hypoxia condition,was examined by scintillation counting. Results Expression of ABCA1 was down-regulated in RAW264.7 cells after being exposed to hypoxia conditon.Meanwhile,cholesterol efflux mediated by ApoA-I decreased after hypoxia treatment. Conclusion Hypoxia could significantly inhibit ABCA1 expression and cholesterol efflux mediated by ApoA-I in RAW264.7 cells.The inhibitory effect of hypoxia on cholesterol efflux may closely correlate with the development of atherosclerosis.