Early care and education (ECE) settings are major developmental contexts for the majority of young children. This chapter presents research on the importance of these settings for child development, covering measures of setting quality and child outcomes in ECE research and empirical studies relating setting quality to child outcomes in depth. One important issue is the consistently significant but small developmental effects of ECE quality. Current research on possible factors contributing to these small associations is outlined, highlighting the potential for child characteristics to interact with setting quality in supporting or undermining child outcomes and the importance of acknowledging the nonrandom ways in which different families come to use different ECE settings (including barriers to obtaining ECE arrangements that are a good fit for the child and family). The chapter ends with a discussion of current practice and policy, featuring mental health consultation models.