Aim Advanced glycation end products(AGE) can induce the intracellular generation of reactive oxygen species(ROS) and cause the dysfunction of endothelial cells.This may accelerate development of vascular atherosclerosis.The source of intracellular ROS in endothelial cells stimulated by AGE was investigated.Methods Human umbilical vein endothelial cells(HUVEC) were cultured and incubated with different concentration of AGE for different time.Intracellular ROS was measured with 2',7'-dichlorodihydrofluorescein diacetate(DCF-DA).rotenone,thenoyltrifluoroacetone(TTFA) and antimycin A as selective inhibitors of mitochondrial complex I,Ⅱ and Ⅲ were used.allopurinol as an inhibitor of xanthine oxidase,Nω-Nitro-L-arginine methyl ester(L-NAME) as an inhibitor of nitric oxide synthase,and diphenylene iodonium(DPI) as an inhibitor of NADPH oxidase were also used.The role of each oxidase in the generation of ROS was observed.Results Intracellular ROS was elevated by the stimulation of AGE.DPI almost completely inhibited the generation of ROS.No significant effect was observed in rotenone,TTFA,antimycin A or allopurinol,while L-NAME increased the level of ROS slightly.Conclusions Tthe results demonstrate that NADPH oxidase is the major source of intracellular ROS in endothelial cells,and the potential targets for the inhibition of the atherogenic signals triggered by AGE.