This review is one component of the HBCC Supply and Quality project, funded by the Office of Planning, Research, and Evaluation in the Administration for Children and Families. This project is summarizing what is known about HBCC supply and quality, developing a research agenda to fill gaps in knowledge, and conducting new research to answer important questions. The findings from this review will: (1) lay critical groundwork to adapt or develop new tools or resources used to assess quality in HBCC settings, (2) guide how the project team approaches measurement in the research agenda, and (3) help early childhood stakeholders and others interested in HBCC quality select measures or indicators for various purposes. (author abstract)