In the spring and fall of 2013, the Center on Education Policy (CEP) convened two meetings of researchers, policymakers, and practitioners to discuss ideas for a more relevant and coordinated research agenda on the Common Core State Standards. Participants in these meetings identified several needs and made a number of thoughtful suggestions. Many agreed there was a need for a synthesis of existing research on the CCSS and their implementation and impact. To help meet this need, CEP has put together this compendium, which very briefly summarizes the published research on many different aspects of the CCSS. The objective was to create an accessible and readable overview of current research that can inform implementation, policy discussions, and the development of future research on the Common Core. Therefore, the creators have intentionally limited the description for each study to one page that summarizes its focus, methodology, and key findings and includes a URL, where available, or a citation. Topics are presented at the top of each study summary. The studies have been categorized based on a broad topics identified by researchers, policymakers, and practitioners as the most relevant and useful areas of study. The compendium is designed to be a living document and will be updated on a rolling basis--this is the second iteration. A list of studies by author is appended.