The liver X receptors(LXR) nuclear receptors are intracellular sensors of cholesterol excess and are activated by various oxysterols. LXRs have been shown to regulate multiple genes of lipid metabolism. After exposure of the cultured THP-1 macrophage-derived foam cells to 22(R)-hydroxycholesterol and 4,4′-diisothiocyanostilbene-2,2′-disulfonic acid (DIDS) respectively at different concentrations for 24 h, cholesterol efflux and liver X receptor α mRNA level were determined by FJ-2107P type liquid scintillator and reverse transcriptase-polymerase chain reaction(RT-PCR), respectively. 22(R)-hydroxycholesterol increases cholesterol efflux in THP-1 macrophage-derived foam cells with dose dependance and DIDS inhibits cholesterol efflux in THP-1 macrophage-derived foam cells with dose dependence too; RT-PCR showed that exposure of the cultured THP-1 macrophage-derived foam cells to 22(R)-hydroxycholesterol and DIDS at different concentrations for 24 h respectively, resulted in increase and decrease respectively in the expression of liver X receptor α mRNA in THP-1 macrophage-derived foam cells with dose dependence. It can be concluded that liver X receptor α plays an important role in cholesterol efflux in THP-1 macrophage-derived foam cells.