The activities of the research group on cancer chemoprevention supported by the Ministry of Health and Welfare of Japan are summarized. Since the research on cancer chemoprevention is quite new in Japan, this paper describes the present status of the development of possible cancer preventive agents. Acyclic retinoid (E-5166) and sarcophytol A encourage further studies. New inhibitory compounds of experimental carcinogenesis, such as cryptoporic acid, oleanolic acid, mokko lactone and ursolic acid were isolated from plants. The importance of the keen collaboration between natural product chemists and clinicians for further meaningful progress in this research field has been emphasized.