Risk estimation and communication are at the center of both challenges. The USPSTF refers to the model developed by Gail and colleagues (16) as one tool for estimating risk. The BCPT used the Gail model to estimate the 5-year incidence of breast cancer for patient accrual on the basis of a woman's age, number of first-degree relatives with breast cancer, nulliparity or age at first birth, number of breast biopsies, pathologic diagnosis of atypical hyperplasia, and age at menarche. For women whose worry results from an exaggerated perception of risk, such estimates may provide reassurance, but the source of anxiety may be more complex than simple misinformation (17). Risk estimates specific to estrogen receptor–positive types of breast cancer would be more helpful. Furthermore, a perspective for good decision making requires 5-year and lifetime mortality estimates not provided by the Gail model. Just as important are estimates over varying periods of incidence and mortality for competing conditions, especially those made more likely by chemoprevention. For example, a stroke or pulmonary embolus confers a high risk for immediate physical disability and death. A diagnosis of breast cancer, distressing as it may be, does not. Therefore, a good decision about chemoprevention requires attention to the timing of harms and benefits as well as to the varied individual preferences concerning any tradeoffs between them.