Of the many novel new cancer therapeutic concepts under development, chemoprevention recognizes that malignancies derive from a long, complex interaction of environmental stress modulated by individual genetic phenotypic expression. As described in depth by Drs. Singh and Lippman in this two-part article, published in last and this month’s issues of oncology, substances with potential chemopreventive activity have been identified from multiple sources. These include: (1) human cancer epidemiology, with an emphasis on dietary assessment, geographic dietary and environmental variation, and differences in cancer incidence among similar regional populations; (2) from mechanistic hypotheses; and (3) clinical observations after treatment of cancer (eg, tamoxifen [Nolvadex] for breast cancer). Drs. Singh and Lippman ably demon-strate the wide variety of sources of potential chemopreventive agents and describe current research studies and outcomes.