The U.S. Centers for Disease Control and Prevention (CDC), which includes the Agency for Toxic Substances and Disease Registry, is recognized as a lead federal agency for protecting the health and safety of people at home and abroad, providing credible information to enhance health decisions, and promoting health through strong partnerships. Research is the foundation of CDC’s success and enables CDC to develop, improve and disseminate evidence-based interventions, programs, and decision support to improve health (Figure I-1). The primary focus of CDC’s research is to fill gaps in knowledge necessary to accomplish the agency’s Health Protection Goals (Chapter II), but it must also be CDC’s core public health mission and be responsive to new opportunities, threats, and future health needs. A recent analysis indicates that the evidence base to support much of public health practice has not kept pace with the growing requirements, and much more research is needed to demonstrate the best methods that support effective public health practices.