Administration of different doses of the diphenol resveratrol had no effect on the growth of an intramuscularly implanted experimental tumour, the Lewis lung carcinoma. These results do not agree with previous reports where a clear effect of resveratrol was shown on tumour burden in both mice and rats. However, administration of the diphenol had a clear anti-metastatic effect, decreasing both the number and the weight of the lung metastases. Similar effects were observed both at 5 and 25mg/kg body weight per day, resulting in an approximately 40% reduction in the number of metastases. These results suggest that resveratrol could be tentatively given as a preventive agent in cancer patients undergoing radiotherapy or chemotherapy.