This study demonstrates that cupric 8-quinolinoxide (CuQ) has induced genetic toxicity in bacteria and mammalian cells through a mechanism of reactive oxygen species (ROS) generation. In the Ames test with rat liver S9, CuQ dose-dependently caused a point mutation in Salmonella typhimurium TA100. The effect of CuQ on DNA damage in HL60 and V79 cells identified in the comet assay is direct and enhanced by the addition of S9. Meanwhile, the tailing length of comet DNA is related to the increasing dosage of CuQ. The genotoxic effect of CuQ on either gene mutation in bacteria or DNA damage in culture cells can be generally blocked by several antioxidants, e.g. pyrrolidinedithiocarbamate, N-acetylcysteine, Vitamins C and E. Supportive of this observation, ROS generation induced by CuQ can be demonstrated both in vitro and in vivo by using the DCFH-DA fluoroprobe. The CuQ-induced intracellular ROS level is also dramatically inhibited by the above antioxidants. Above results imply that the CuQ-induced genotoxicity could be mediated by ROS generation. The nature of ferrous-dependent and S9-enhancing in CuQ-induced ROS generation hints a Fenton-like reaction or some specific enzymes activation could be involved in this process. Furthermore, a DNA damage- and oxidative stress-dependent protein, P53, could also been induced by CuQ treatments in a time-course and dose-dependent manners. Its expression level is recoverable by antioxidants too. In conclusion, our current study strongly suggests that CuQ induces gene mutation, global DNA damage, and P53 expression through a ROS-dependent mechanism.