The purpose of this investigation is to report about study identification practices across evidence-based registries and clearinghouses in social policy fields, which serve as a resource for scientific, evidence-based decision-making about practices about desired outcomes in these social policy fields. The information retrieval procedures of the What Works Clearinghouse will be described in detail. Using the general study identification and search procedures for the WWC and other evidence-based repositories, the presenters will highlight how differences in comprehensiveness and transparency can result in different studies available for review and synthesis. Study identification practices from eight evidence registries will be analyzed and reported. The registries to be included are: (1) Blueprints for Healthy Youth Development, (2) the California Evidence-Based Clearinghouse (CEBC), (3) the Coalition for Evidence-Based Policy, (4) CrimeSolutions.Gov, (5) National Registry of Evidence-Based Programs and Practices (NREPP), (6) the Promising Practices Network (PPN), (7) What Works in ReEntry, and (8) What Works Clearinghouse (WWC). A table provides a summary of the general study identification practices for the evidence-based repositories included in this investigation. It was found that among these eight registries, four use literature reviews, three use nominations, and one uses a combination of literature reviews and nominations for study identification. Four registries conduct searches for studies by topic area or outcome; and four registries conduct searches by programs or interventions, and then apply study appraisal guidelines. Three registries specify that publications must be in English in a peer-reviewed journal or other professional publication, or comprehensive evaluation report (Crimesolutions.gov, National Registry of Evidence-Based Programs and Practices, and What Works Clearinghouse). One registry specifies studies must be in peer-reviewed journals (California Evidence-Based Clearinghouse). Unpublished studies may be considered by Blueprints, the Coalition for Evidence-Based Policy, and the Promising Practices Network (if publicly available).