Anti-cancer activities of resveratrol (3,4',5-trihydroxylstilbene) have attracted extensive research attention. Suppression of pulmonary metastasis of BALB/c mice challenged with CT26 colorectal adenocarcinoma cells achieved by oral administration of resveratrol was assessed in three separate experiments. Each mouse was challenged by tail vein injection with CT26 cells. Prior to challenge, 8-wk-old mice were fed with a basal diet and orally administered with resveratrol (30 mg/kg/2 days) eight or twelve times. After challenge, oral administration of resveratrol was continued until mice were sacrificed on day 20. As integrated from three experiments, 3.7% of the control mice (n=27) and 68.7% of the resveratrol-treated mice (n=26) exhibited free of metastasis. In a second study, 8-wk-old BALB/c mice were orally administered with resveratrol 12 times and challenged with CT26 cells for 100 days. All control mice died but 50% of the resveratrol-treated mice survived. The surviving mice were challenged with CT26 cells by hypodermic injection, fed with a basal diet for an additional 30 days, and sacrificed. Tumor lumps or nodules were not detected at the injection sites or in the lungs. This reveals that intrinsic vaccination-like defense has resulted from administration of resveratrol and challenge of tumor cells.