The comprehensive workbook includes clear guidance and rationale along with a substantial set of customizable tools for defining at-risk populations in a given jurisdiction and providing outreach. The process of defining populations is presented without dogma and is intended to be informed by local data and experience. While anyone could use the workbook, the workbook would probably be most useful and engaging to someone already involved in qualitative research among at-risk populations. The workbook was informed by literature review and interviews with government and community leaders. State and local health departments have used and reviewed it extensively (in draft form). This tool was identified through NACCHOs Resource Portfolio Project on the CDC Public Health Preparedness Capabilities. Through this project, NACCHO worked with the Center for Infectious Disease Research and Policy (CIDRAP) to identify, research, and validate tools, practices, and products that can assist LHDs to address challenges in meeting select PHEP capabilities.