Chemoprevention has been shown to be an extremely promising approach to the prevention of invasive cancer. Through the identification of chemopreventive agents that inhibit or reverse the process of carcinogenesis, new strategies of early intervention can be developed for patients at high risk that potentially prevent the onset of invasive and metastatic phases of cancer. This articles reviews the present efforts in chemoprevention research, including the identification of promising agents, screening, and preclinical and clinical evaluations.