Background Studies have shown that oxidized low density lipoprotein (ox-LDL) promotes the pathogenesis and development of atherosclerosis (AS), and that the proliferation, migration and phenotype alteration of vascular smooth muscle cells (vSMCs) into foam cells are critical changes in AS. It is proposed that ox-LDL might play a novel role in the pathologic process of vSMCs. The present study was performed ex vivo to investigate the effects of ox-LDL on the growth of cultured human vSMCs.Methods Using NaBr density gradient centrifugation, LDL from human plasma was isolated and purified. ox-LDL was produced from LDL after being incubated with CuSO4. ox-LDL was then added to the culture medium at different concentrations (25 μg/ml, 50 μg/ml, 75 μg/ml, 100 μg/ml, 125 μg/ml, and 150 μg/ml) for 7 days. The influence of ox-LDL on vSMC growth was observed from several aspects as growth curve, mitosis index, lipid staining, and in situ determination of apoptosis. The digital results were analyzed with SPSS 10.0.Results The ox-LDL produced ex vivo had a good purity and optimal oxidative degree, which was similar to the intrinsic ox-LDL in atherosclerotic plaque. ox-LDL at a concentration of 25 μg/ml demonstrated the strongest proliferation. At the concentration of 125 μg/ml, ox-LDL suppressed the growth of vSMCs. At concentrations of 25 μg/ml and 50 μg/ml, ox-LDL presented powerful mitotic trigger. When the concentration of ox-LDL increased, the mitotic index of vSMCs decreased gradually. ox-LDL induced more foam cells from vSMCs with rich intracellular lipid accumulation at concentrations of 25 μg/ml and 50 μg/ml. ox-LDL at higher concentrations induced more apoptotic vSMCs.Conclusions ox-LDL at lower concentrations may trigger proliferation and phenotype alteration into foam cells of vSMCs, and at higher concentrations it may induce apoptosis in vSMCs. ox-LDL plays an important role in the pathogenesis and development of atherosclerosis by its effect on vSMCs proliferation, phenotype alteration and apoptosis.