public health preparedness ■ Abstract Threats to Americans' health-including chronic disease, emerging infectious disease, and bioterrorism-are present and growing, and the public health system is responsible for addressing these challenges. Public health systems in the United States are built on an infrastructure of workforce, information systems, and organizational capacity; in each of these areas, however, serious deficits have been well documented. Here we draw on two 2003 Institute of Medicine reports and present evidence for current threats and the weakness of our public health infrastructure. We describe major initiatives to systematically assess, invest in, rebuild, and evaluate workforce competency, information systems, and organizational capacity through public policy making, practical initiatives, and practice-oriented research. These initiatives are based on applied science and a shared federal-state approach to public accountability. We conclude that a newly strengthened public health infrastructure must be sustained in the future through a balancing of the values inherent in the federal system.