U.S. government policy has sought alternatively to improve the circumstances of single parent families and to reduce their numbers. There now is growing interest in interventions seeking to promote healthy marriages, and, where marriage is infeasible, strengthen relationships between unmarried parents. These interventions will stand a better chance for success if they are based on a sound understanding of the determinants of union formation, stability, and quality. The Administration for Children and Families (ACF) is the lead federal agency charged with developing and testing initiatives in this area. Mindful of the need for strong basic empirical foundation for policies and programs, ACF commissioned Abt Associates Inc. to review the evidence on important determinants of marriage and cohabitation among disadvantaged Americans. The objectives of this project were to (1) assess findings and gaps in basic research literature and (2) provide a guide to major national survey data that could be used to close the gaps. This report — which documents nine key surveys — fulfills the second of these objectives. We start by defining the topics of analysis that this guide was designed to address. Then, we describe some of the desirable attributes of data sets for research in this area. Next, we identify the datasets included in the guide and comment on several useful datasets that we were not able to include. The body of this report is comprised of separate chapters on each of the nine selected surveys. Separate sections detail key aspects of each survey, including its design, general content, utility for research on marriage and cohabitation outcomes and determinants, and data availability. Accompanying exhibits provide additional detail on survey content. Where possible, these exhibits have been taken directly from survey documentation. In the concluding chapter, we provide discussion across the nine surveys of the degree and ways in which they can be used to address major gaps in knowledge of marriage and cohabitation determinants. Sections correspond to the ten broad themes we investigated for the literature review component of this project. (Author abstract)