A nod of approval from a U.S. Food and Drug Administration advisory committee means that tamoxifen, a powerful drug now given to some women to prevent a recurrence of breast cancer, may soon become the first such drug given to women who have not had breast cancer, in order to stave it off in future. That department, if it is approved, opens a new realm of possibly effective and certainly terrifying decisions and trade-offs that are likely to confront patients.(editorial)