Aim To study the effect of stromal cell derived factor 1 alpha(SDF-1α)on CXCR4 expression in THP-1 monocyte,and the effect of SDF-1α and CXCR4 antibody on monocyte/endothelium adhesion.Methods CXCR4 mRNA and protein expressions were detected by RT-PCR and Western blotting respectively in moncyte pretreated with 100 μg/L of SDF-1α for 0 and 30 min.ECV-304 endothelial cells pretreated with 0,50,100 and 200 μg/L SDF-1α for 30 minutes and sub-incubated with THP-1 cells,with or without CXCR4 antibody(10 mg/L),THP-1/ECV-304 adhesion was observed.Results CXCR4 was constitutionally expressed in THP-1 cells and increased remarkably by 100 μg/L SDF-1α for 30 min.THP-1 and ECV-304 adhesion was enhanced by 50～200 μg/L SDF-1α,but it was also apparently inhibited by the CXCR4 antibody(P<0.05).Conclusions SDF-1α enhances CXCR4 expression in THP-1 cells.SDF-1α enhances monocyte/endothelium adhesion,which is related to up-regulating CXCR4 expression.