This study was conducted to investigate the effectiveness of pumpkin powder in the diet of experimental animals on chemically induced stomach and mammary canceers. Three weeks old male SpragueDawley rats were randomly allocated to either 1) basal diet+MNNG, 2) basal diet+MNNG+PMC, 3) 2.5% pumpkin powder supplemented diet+MNNG+PMC, or 4) 5.0% pumpkin powder supplemented diet+MNNG+PMC for stomach cancer experiment. And female Sprague-Dawley(5 weeks old) rats were randomly assigned to either 1) basal diet only, 2) basal diet+DMBA, 3) 2.5% pumpkin powder supplemented diet+DMBA, or 4) 5.0% pumpkin powder supplementd diet+DMBA. In both experiments, supplements of pumpkin powder in basal diet decreased body weight of both male and female experimental animals. Pumpkin powder in rat diet decreased significantly(p<.05) chemically induced stomach cancer. With its suppressing effects on stomach cancer, pumpkin powder in diet of experimental rats had decreasing effects on the initiation and development of DMBA-induced mammary cancer. In conclusiion, current study may provide in vivo data to develop health foods using pumpkin. Further studies, however, are essential to clarify the exact role of pumpkin powder in chemically induced stomach and mammary cancers.