Objective: This study aimed to investigate the antitumor effects of water extracts of Panax notoginseng (WEPN) in NCI-H460 human lung cancer cell xenografted nude mice. Materials and Methods: We cultured NCI-H460 cell lines and xenografted them to nude mice. The mice were divided into 3 groups; positive control group, NCI-H460+150 mg/kg WEPN-treated group, and NCI-H460+300 mg/kg WEPN-treated group. They had been raised and treated in 28 days. We checked their body weight and tumor weight and volumes twice a week and their absolute organ weight and microhistological observation at the final day. We also calculated their tumor inhibition rate (I.R.), mean survival time and percent increase in life span (% ILS). Results: Body weight of WEPN (300 mg/kg) treated mice tended to slightly greater increase than those of the positive control group, but had no significance. Tumor volume (measurement with a caliper) of WEPN-treated mice tended to be lower than that of the positive control group. Inhibition rate (I.R.) of the WEPN group decreased more than the positive control group, but had no significance. Results of tumor weights and volume (plethysmography) had no significance. Mean survival time and percent increase in life span (% ILS) in the WEPN 300 mg/kg treatment group were higher than those of any other group (p<0.05). In absolute organ weights, the WEPN (150-300 mg/kg) treatment group decreased liver weights (p<0.05). Liver tissue of mice treated with WEPN (300 mg/kg) did not show any specific lesions. Conclusion: We suggest that WEPN may have potential as a growth inhibitor of solid tumors induced by NCI-H460 without any side effects. However, this study has limitations in proving anti-tumor effects of WEPN, so further studies to overcome those limitations will be needed.