In order to investigate the potential toxicity of nano-sized lead dioxide (PbO2) in adult mice,we compared the distribution of 60nm PbO2 to their corresponding chemical (lead dioxide) at a con stant PbO2 nanoparticles dose,and determined the inherent differences between these two classes of materials.Mice were randomly divided into five groups: control group and four treatment groups (200mg/kg body weight PbO2,50,100 and 200mg/kg body weight 60nm PbO2 groups).Chemicals were administrated to mice via oral gavage,once a day and for 5 consecutive days.Our data showed that Pb dose-dependently accumulated in liver,kidney,cortex and hippocampus after PbO2 nanopar ticles exposure.The PbO2 nanoparticles induced the hepatotoxicity and nephrotoxicity, and induced oxidative stress in liver,kidney and brain tissues in mice.Compared with that of PbO2,PbO2 nanop articles induce severer hepatotoxicity,nephrotoxicity and oxidative damage at the same dose.