Public health is a dynamic field. Outbreaks of new diseases, as well as changing patterns of population growth, economic development, and lifestyle trends all may threaten public health and thus demand a public health response. As the practice of public health evolves, there is an ongoing need to reassess its scientific, ethical, legal, and social underpinnings. Such a reappraisal must consider the disagreement among public health officials, public health scholars, elected officials, and the public about the proper role of public health and the distinctions, for example, between public health and clinical care, and public health and health promotion.In this article I will attempt to characterize the main points of contention as well as offer my own views regarding the proper scope of public health. Greater clarity and consensus on the meaning of public health are likely to lead to more efficient and effective public health interventions as well as increased public and political support for public health activities.