Aim To understand whether lipid peroxidation injury to endothelial cells ( ECs ) induces the production of monocyte chemotactic factor RANTES. Methods After a four hour exposure of the cultured human umbilical vein ECs to 5 μmol/L diamide, the conditioned medium (CM) was collected. To obtain a conditioned medium containing RANTES (MW 8 kDa ), the above CM was put into the double layer dialysis molecular porous membrane tubings (Spectrum Lab. Inc. ) with the molecular weight cut off at 10 kDa ( inner layer ) and 3.5 kDa ( outer layer ) respectively. Appropriate amount of 0.01 mol/L PBS was injected into the interspace between the two membranes. The whole set of the membrane tubings was suspended in a pyramid flask containing PBS, and then the samples were dialysed against PBS. Finally, a conditioned medium with MW of 3.5～10 kDa was taken out from the interspace between the two membranes. The chemotactic activity of this conditioned medium for monocytes was tested by micropore filter method using a modified Boyden chamber. For antibody inhibition studies, the conditioned medium was incubated with anti-RANTES antibody and assayed again. Results The monocyte migration distance induced by diamide-CM group (89.75±11.33 μm) is markedly longer than that of the nondiamide-CM group(77.30±11.53 μm)and that of the random migration group(76.18±10.50 μm ). Analysis of variance showed that there was a significant difference between groups(F=47.20,P<0.01). After the addition of anti-RANTES antibody, monocyte chemotactic activity was markedly inhibited (F=21.31,P<0.01 ). Conclusion On the basis of functional assay it suggests that lipid peroxidation injury might induce ECs to produce increased RANTES and may play an role in the recruitment of monocytes into the intima in atherogenesis.