Aim: To determine whether the antitumor factor nm23 is related with antioxi-dation. Methods: Full-length human nm23-Hl was cloned into a mammalian-expressing vector and transiently introduced into HeLa cells. Results: A remark-ably low level of reactive oxygen species (ROS) was detected in the cells over-expressing nm23-Hl. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and trypan blue assays found that the cells transfected with a nm23-H1-expressing plasmid had higher viability and stronger resistance to oxidative stress. Immunoprecipitation tests revealed that endogenous nm23-H1 formed a protein complex with p53. Furthermore, the intracellular levels of p53 and p53-regulated gene GPXI were obviously increased in the cells overexpressing nm23-H1. The downregulation of p53 in the cells overexpressing nm23-H1 resulted in a higher cellular ROS level and lower cell viability. Conclusion: The findings suggest that nm23-H1 may act as a cellular protector against oxidative stress, possibly triggering the p53-related antioxidative pathway.