ln their review of school readiness indicators, Phillips and Love (1997) anticipated major data collection efforts that would increase the depth and breadth of measures of school readiness available at the national level and that might be used for monitoring of progress toward school readiness at a more local level. Substantial progress has been made in the measurement of school readiness in the last 10 years, and we are now at the point of beginning to harvest the results of such efforts. This chapter is organized to provide an overview of the conceptualization of school readiness and a review of major recent developments in the measurement of school readiness at the national and state levels. In addition to reviewing progress, it notes gaps and issues to address in further work. (author abstract)