Objectives: This report details development of the 2013 National Center for Health Statistics' (NCHS) Urban-Rural Classification Scheme for Counties (update of the 2006 NCHS scheme) and applies it to health measures to demonstrate urban-rural health differences.Methods: The methodology used to construct the 2013 NCHS scheme was the same as that used for the 2006 NCHS scheme, but 2010 census-based data were used rather than 2000 census-based data. All U. S. counties and county-equivalent entities are assigned to one of six levels (four metropolitan and two nonmetropolitan) based on: 1) their February 2013 Office of Management and Budget designation as metropolitan, micropolitan, or noncore; 2) for metropolitan counties, the population size of the metropolitan statistical area (MSA) to which they belong; and 3) for counties in MSAs of 1 million or more, the location of principal city populations within the MSA. The 2013 and 2006 NCHS schemes were applied to data from the National Vital Statistics System (NVSS) and National Health Interview Survey (NHIS) to illustrate differences in selected health measures by urbanization level and to assess the magnitude of differences between estimates from the two schemes.Results And Conclusions: County urban-rural assignments under the 2013 NCHS scheme are very similar to those under the 2006 NCHS scheme. Application of the updated scheme to NVSS and NHIS data demonstrated the continued usefulness of the six categories for assessing and monitoring health differences among communities across the full urbanization spectrum. Residents of large central and large fringe metro counties differed substantially on many health measures, illustrating the importance of continuing to separate these counties. Residents of large fringe metro counties generally fared better than residents of less urban counties. Estimates obtained from the 2013 and 2006 schemes were similar.