Objective: To observe inhibitory effect of intercellular adhesio n molecule-1(ICAM-1) antisense DNA on ICAM-1 expression in endothelial cells. Methods: ICAM-1 antisense DNA vector was constructed and transfe cted into endothelial cells by lipofectamine reagents. ICAM-1 expression was me asured by flow cytometry in endothelial cells and transfected cells with or with out TNFα. Results: Agarose gel electrophoresis showed 1.4 kb ICAM -1 DNA was inserted into pcDNA3 expression vector in reverse direction. ICAM-1 expression in normal cells with the stimulation of TNFα was significantly high er than without the stimulation(P<0.01). There was no significant increase in ICAM-1 expression in transfected cells with the stimulation of TNFα(P> 0.05). ICAM-1 expression in transfected cells was lower than that in normal cel ls(P<0.05). Conclusion: ICAM-1 expression in endothelial cell s can be inhibited by ICAM-1 antisense DNA in vitro.