This project was performed under a contract from the Agency for Healthcare Research and Quality (AHRQ) in collaboration with the Centers for Medicare & Medicaid Services (CMS) through the Developing Evidence to Inform Decisions about Effectiveness (DEcIDE) Network of AHRQ’s Effective Health Care (EHC) Program. The purpose of the project was to update and expand Registries for Evaluating Patient Outcomes: A User’s Guide. The User’s Guide was first published in 2007 as a reference for establishing, maintaining, and evaluating the success of registries created to collect data about patient outcomes. The second edition, which provided updates to the existing topics and addressed four new topics, was published in 2010. The purpose of this revised and expanded third edition is to incorporate information on new methodological and technological advances into the existing chapters and to add 11 new chapters to address emerging topics in registry science.