Aim Oxyresveratrol (trans2,3 , 4,5tetrahydroxystilbene, OXY) , a natural polyphenolic phytochemical presents in mulberry (Morus alba L.), has been reported to have various bioactivities.Though OXY has high structural similarity with resveratrol, which has been identified as a chemopreventive agent, little is known about OXY s effect on cancer.The main objective of our study was to investigate the effect of OXY on metastasis in vivo.To establish an experimental metastasis model, male Kunming mice were challenged with H22 cells by tail vein injection, and were given different doses of OXY (20, 40,80 mg · kg1 body weight per day) for 14 days intraperitoneally.Administration of OXY showed a clear antimetastatic effect.Compared to control group (n =10) ,the numbers of pulmonary nodules and lung weight were significantly decreased in mice of 40 mg · kg1 group (n =10, P < 0.05), which results in 54.5% reduction in the number of metastases.Similar inhibitory effects were observed both at 20 and 80 mg · kg1 groups(n =10, 34.2% and 35.7%, respectively).OXY at the doses used caused an increase in spleen index (P < 0.05) but not thymus index.Further we observed animal body weights loss and food intake decrease (P < 0.05), suggesting the toxicity of high dose used.Therefore, we suggest that oxyresveratrol may benefit human as a new preventive agent for cancer metastasis.