Objective: This study was designed to approach the hypothesis that oxidative stress mediates chromium-induced cytotoxicity on the nervous system.The results from this in vitro study may be used to gain an insight into the mechanism of chromium-ioninduced neurotoxicity and evaluate the safety of MM prostheses on the nervous system.Methods: PC12 cells were used as neuronal cell model and were exposed to 0.1-20μmol/L Cr6+and 25-300 μmol/L Cr3+ions for 24-72 h.Cytotoxicity were assessed using the MTT assay and LDH assay.Morphological changes were observed by microscopy.