The National Public Health Performance Standards Program (NPHPSP) has developed assessment instruments based on the ten essential public health services (EPHS) for state and local health departments. The article reviews validity testing of the state and local instruments. The study employed multiple approaches to validity testing with state and local health departments in Florida, Hawaii, Minnesota, Mississippi, and New York. The New York State validity checks included the judgments of community partners. The study found that the EPHS have content and face validity as a basis for measuring public health system performance. The article includes recommendations for continued development of the NPHPS.