This report provides the results of a national scan of measures being used by early childhood systems and initiatives to gauge the well-being of young children and their families. The purpose of the project was to better understand the state of the field and to identify opportunities to drive improvements in measurement that could help contribute to better early childhood outcomes. Over the past decade, the authors have seen the rapid spread of early childhood systems and initiatives. Each of these efforts has developed its own set of measures to understand and assess children's well-being and to observe changes over time. The authors reviewed 39 such measure sets, attempting to include as many of the initiatives as possible touching on early childhood and a significant, but by no means exhaustive or representative, sample of state and local early childhood systems. Even this limited scan produced more than 500 measures for review. The authors classified each of the measures in three ways: (1) Domains; (2) Categories; and (3) Concepts. The document is organized as follows: (1) Conclusions; (2) Summary tables; (3) Methodology in the metrics scan; and (4) Detailed listing of all the measures reviewed. [This report was prepared by National Institute for Children's Health Quality (NICHQ).]