OBJECTIVE Angiogenesis is critical not only for growth of primary tumors but also for cells established at distant organs. We investigated the effects of angiogenesis inhibitor, TNP-470, on the establishment and growth of intraperitoneally inoculated human gastric cancer cell line, MKN-45, and survival of nude mice with this tumor. METHODS Human gastric cancer cell line, MKN-45, were injected into the peritoneal cavity of an ICR nude mouse and a model of peritoneal dissemination was developed. TNP-470 was injected subcutaneously every other day from day 1 until sacrifice or death. The effects of TNP-470 on MKN-45 cells were also examined in vitro. RESULTS Although the number of disseminated foci was not significantly different, the maximum size was significantly smaller in a TNP-treated group than those of a control. Survival time was significantly longer in a TNP-treated group. TNP-470 demonstrated no growth inhibition of MKN45 cells in vitro. CONCLUSIONS Those results suggested that anti-angiogenic agent, TNP-470, might be effective in treating peritoneal dissemination of gastric cancer by inhibiting growth of the seeded tumor cells on the peritoneum.