The use of patient navigators—individuals who help patients to receive the care they need, such as help getting to appointments and overcoming obstacles that may delay care—holds great promise in improving health care. Several studies1-3 have found patient navigation to be effective for cancer screening,yet numerous unanswered questions confront the care system and policy designers. For whom is navigation effective and how great of a difference does it make? Can we afford to hire navigators and how many people can a navigator manage? Is employing patient navigators cost-effective and how much better is it than various less-intensive approaches to improving adherence?