The National Institute of Standards and Technology (NIST) Measurements and Standards Laboratories (MSL) provide technical leadership for the nation's measurement and standards infrastructure and assure the availability of essential reference data and measurement capabilities. At NIST's request, the National Research Council (NRC) carries out a biennial assessment of the seven MSL. The assessment focuses on each laboratory's technical quality and merit; and effectiveness. It also examines the relevance of the NIST programs and how well laboratory facilities, equipment, and personnel are able to fulfil the MSL mission. This report presents an overall assessment of the MSL followed by detailed assessments of each of the seven laboratories.