The spectrum of infectious disease is changing rapidly in conjunction with dramatic societal and environmental changes. Worldwide, explosive population growth with expanding poverty and urban migration is occurring; international travel and commerce are increasing; and technology is rapidly changing, all of which affect the risk of exposure to infectious agents. Infectious diseases are emerging, re-emerging, and increasing in the United States, taking a toll in both morbidity and mortality. A major cause of the emergence of new diseases is environmental change (for example, human encroachment into wilderness areas and increased human traffic through previously isolated areas). The re-emergence of some diseases can be explained by evolution of the infectious agent (for example, mutations in bacterial genes that confer resistance to antibiotics used to treat the diseases). In partnership with representatives from health departments, other federal agencies, medical and public health professional associations, and international organizations has developed a strategic plan to address emerging infectious disease threats. The plan contains four goals that emphasize surveillance, applied research, prevention and control, and public health infrastructure. To ensure sustainability, plan implementation will be approached in stages, as a long-term endeavor with emphasis on extramural programs. As health-care reform proceeds priority should be given to strengthening partnerships between health-care providers, microbiologists, and public health professionals to detect and control emerging and re-emerging infectious diseases.