Improving the quality of health care requires going beyond the basic standards for health care organizations and formal clinician education. One potential strategy to improve health care quality is credentialing. Credentialing describes specific processes that involve licensure, certification, registration, and accreditation (NOCA, 2005; Styles and Affara, 1998). Currently, only limited information is available about the relationship between credentialing and the quality of care, practice, or patient outcomes. The path to building credentialing evidence is difficult. This is because the process of working toward and having certain credentials may support clinical decision making and the goals of quality, safety, and efficiency of health care (Hickey et al., 2014), while the process of attaining or possessing a credential may serve as a mediating, moderating, or modifying variable in research analyses. Credentialing requirements for individual health care clinicians and health care organizations vary (Kendall-Gallagher and Blegen, 2009), as do evaluation processes and the type of data collected for different credentialing programs. Several organizations are involved in credentialing programs, including the National Committee for Quality Assurance, the Joint Commission, URAC (formerly known as the Utilization Review Accreditation Commission), and the American Nurses Credentialing Center (ANCC). These programs oversee credentialing and qualification standards for health care organizations and individual clinicians. Organizations that manage credentialing processes typically evaluate the training and skill level of individuals and organizations, as well as their capacity to meet certain standards (ICN, 2009). However, each organization sets the standards for the elements within their respective credentialing program, and determines which data elements are to be collected, maintained, and updated. Similar data are not available for organizations and individuals without credentials. As a result, scientists lack both the data and the data harmonization required to determine the impact of credentialing in general, or to compare the impact of specific credentials on individual and organizational outcomes. Progress in credentialing research is currently obstructed by datasets that are both insufficiently accessible and inadequately standardized across credential types and credentialing organizations. To gain an understanding of the impact credentialing has on health care organizations, patients, and clinicians, researchers must have access to data that are standardized, accessible, and up to date, as well as defined and consistently structured. Additionally, data must report on organizations and individuals with and without credentials or credentialing programs. Data that meet these criteria can be used to identify trends, enable decision making, and permit the analysis of outcomes. Research findings based on data that do not meet these criteria will be inconclusive, as it will be impossible to distinguish between results ...