This Guide is an annotated bibliography of existing large scale data sets that provide useful information to policymakers, researchers, state administrators, and others in the field of child care and early education. The Guide follows an ecological approach to research and policy in the field: it brings attention not only to children themselves, but also to the different contexts in which they grow and develop, in hopes of promoting research and decision making that take into account the interrelations among those contexts and how these impact on children. The Guide consists of profiles indicating whether each data set offers information on the use and characteristics of child care and early education, as well as on child, family, household, school, and community characteristics. Also included is a reference list of resources that use these data sets and are part of "Research Connections". The update of this Guide describes data sets that are publicly available, do not require the payment of fees, have a fairly comprehensive content, and are of value for policymakers and researchers.