The Centers for Disease Control and Prevention's National Public Health Performance Standards Program (NPHPSP) has developed instruments to measure the performance of local and State public health departments on the 10 'Essential Services of Public Health.' This article is a report of the evaluation of the content and criterion validity of the local public health performance assessment instrument, and the content validity of the State public health performance assessment instrument. The NPHPSP standards based on the Essential Services have validity for measuring local public health system performance, according to community partners. The model standards are valid measures of State performance, according to State public health departments in three States. Within the scope of the validity evaluations completed, the NPHPSP State and local performance assessment instruments were found to be valid measures of public health performance.