Nanoscale materials (such as TiO2, hydroxyapatite nanoparticles) have gained much concern in the coating of implants for cell adhesion and growth to improve the osteoconductivity. However, due to attrition and corrosion, the wear particles would be generated from the joint in living organism, and influence the physiological function of synovial membranes in joint cavity. In this study, the potential cytotoxicity of anatase TiO2 nanoparticles (TiO2 NPs) on rat synovial cell line 364 (RSC-364) was investigated. After treatment with different concentrations of TiO2 NPs (0, 3, 30, 300 microg/ml), the viability of RSC-364 cells were decreased in a dose-dependent manner. TiO2 NPs exposure could disrupt the integrity of cell plasma membrane, leading to the increased leakage of lactate dehydrogenase (LDH) into the culture medium. TiO2 NPs were uptaken by RSC-364 cells. The ultrastructure of RSC-364 cells was changed such as nuclear shrinkage and mitochondrial swelling. The reactive oxygen species (ROS) was over-produced especially in the cells exposed to 30 and 300 microg/ml TiO2 NPs. The activities of endogeneous antioxidant enzymes, superoxide dismutase (SOD) and catalase (CAT), were significantly decreased. The increased lipid peroxidation product (malondialdehyde, MDA) suggests the oxidative damage in cells. The flow cytometry detected that the cell cycle was blocked in G0/G1 phase, inhibiting the cell proliferation. These preliminary results indicate the oxidative stress injury and cytotoxicity of anatase TiO2 NPs on rat synovial cells. The reasonable and safe application of nanomaterials in artificial implants needs further study.