Precancer or intraepithelial neoplasia (IEN) is a noninvasive lesion that has genetic abnormalities, loss of cellular control functions, and some phenotypic characteristics of invasive cancer and that predicts for a substantial likelihood of developing invasive cancer. The AACR Task Force on the Treatment and Prevention of IEN has delineated the relationship between IEN and cancer risk as well as the clinical benefit that can be derived from reducing IEN burden. Although several effective endoscopic and surgical treatments for IEN have become standard medical practice, these interventions can confer morbidity and do not treat the entire epithelial field at risk. The incidence of many epithelial cancers is continuing to rise, the number of individuals at risk is increasing with the aging population, and the rapid advancement of imaging and molecular diagnostics is bringing to light precancers that were heretofore clinically silent. There is therefore an urgent need to rapidly develop new treatment and prevention agents for IEN. The AACR IEN Task Force recommends focusing on established precancers as the target for new agent development because of the close association between dysplasia and invasive cancer and because a convincing reduction in IEN burden provides patient benefit by reducing cancer risk and/or by decreasing the need for invasive interventions. The IEN Task Force proposes several clinical trial designs that provide practical and feasible approaches to the rapid development of new agents to treat and prevent precancer.