In an increasingly complex and varied world of public health threats, there is a clear need for an effective public health system. One way to address the current challenges facing public health is to look at the quality and preparedness of the public health workforce and at the relevance and quality of public health education and training. In "Who Will Keep the Public Healthy," the Committee on Educating Public Health Professionals for the 21st Century, under the Institute of Medicine (IOM), examines the education of public health professionals and directs recommendations for strengthening public health education, research, and practice at schools of public health, related schools and institutions, and public health agencies. The committee identified six major responsibilities for schools of public health: (1) educate the educators, practitioners, and researchers, and prepare public health leaders and managers; (2) serve as a focal point for multi-school transdisciplinary research, as well as traditional public health research to improve the health of the public; (3) contribute to policy that advances the health of the public; (4) work collaboratively with other professional schools to assure quality public health content in their programs; (5) assure access to life-long learning for the public health workforce; and (6) engage actively with various communities to improve the public's health. Suggestions for public health agencies range from engaging in faculty and staff exchanges with schools of public health, to assure that those in public health agency leadership positions are professionals with M.P.H.-level educations or experience in the ecological approach to public health. Previous efforts to improve public health education, research and practice fell short due to lack of political will, public disinterest, and insufficient funds. This publication emphasizes the need for timely action in order to move toward 21st century public health goals.