Aim The purpose of this study was to investigate the effect of L-arginine on oxidized low density lipoprotein(OLDL)induced monocytes adhesion and vascular cell adhesion molecule-1(VCAM-1 )expression in cultured porcine aortic endothelial cells.Methods The porcine aortic endothelial cells (EC)were isolated using an enzyme dispersal method,and cultured in M199 cell culture media containing 20% fetal bovine serum.Monocytes(MC)were isolated from normal human blood by Ficoll-Hapaque density grade centrifugation. Human oxidized LDL was obtained from normal human plasma by ultracentrifugation,and oxidized by Cu2+.The effect of L-arginine on OLDL mediated EC-MC adhesion was determined by analysing protein contents of cells.Vascular cell adhesion molecule-1 mRNA expression in EC was determined by reverse transcription polymerase chain reaction (RT-PCR ).Results Treatment of EC with OLDL led to an increase in VCAM-1 mRNA expression and adhesion rate of monocyte in dose-(0. 05, 0.1 and 0.2 MIL)and time-(2,4 and 6 h)dependent manners. L-arginine inhibited the expression of VCAM-1 in EC and adhesion of MC induced by OLDL also in a dose-(1,2and 4 mmol/L)and time(2,4 and 6 h)dependent manners.Conclusion The effect of L-arginine on OLDL induced monocyte adhesion is associated with a reduction of VCAM-1 expression in endothelial cells.