Description: This Issue Brief is an overview of research related to the measurement of quality in child care and early education settings, including important aspects of quality to measure, aspects of quality that existing measures cover well and effective strategies for measuring quality in state quality rating and improvement systems. This brief provides an overview of what we know and what we don’t know, given the current status of the research, about three key questions concerning the measurement of quality. It also provides suggestions for ongoing research and dialogue related to each question.