PURPOSE: The metastatic animal model of human cancer is important from a practical point of view in the research of cancer metastasis, because it resembles the original tumors morphologically, biologically and biochemically. We developed the animal model to investigate the clinically relevant metastasis of gastric cancer which is the leading cause of death in Korea. METHODS: Seven to eight-week-old specific-pathogen-free (SPF) BALB/c-nu mice were used. We developed an orthotopic transplantation model using the tissue obtained from an inoculation of the gastric cancer cell suspension (YCC-3) into a subcutaneous layer of mice. The mice were kept in laminar-flow cabinets under SPF condition and inspected everyday. RESULTS: Mice were sacrificed 8~12 weeks after the operation when they showed either a measurable mass or signs of distress. The metastatic pattern of this animal model was very similar to that of human gastric cancer. At autopsy, the local growth of the gastric cancer, lymph node metastasis and any distant metastasis were noted. CONCLUSION: We developed an animal model for human gastric cancer metastasis that will enhance our understanding of the biology of cancer metastasis and it will contribute to the development of the research and treatment of cancer metastasis.