The NPPES is often used as a workforce dataset as a National Provider Identifier (NPI) is required to bill Medicare, Medicaid, and most private insurers. This dataset does have inherent disadvantages when being used as a workforce dataset. (1) There is no indication if the provider is currently delivering direct patient services or if they have moved to an administrative function, retired, or are no longer practicing. (2) Full Time Equivalent (FTE) percentages are not included in the data. (3) Unlike licensure data there is little need to update deactivation of a NPI on a regular basis. (4) Data (including practice addresses) are reported by the provider or an authorized party which may not accurately reflect a provider’s actual practice location. These limitations highlight the overrepresentation of available providers when using NPPES as a workforce dataset. Some of these limitations may be resolved by linking NPPES to other data sources such as the AMA Masterfile which includes licensure, membership and certification data creating a more accurate picture of practicing PCPs. However, an analogous linkage for BHPs is virtually non-existent (Holzier, Goldsmith & Ciarlo, 2000).