Migration shapes societies. Its economic, social and demographic impacts are large and increasing. Policymakers, researchers and other stakeholders need data on migrants – how many there are, their rates of entry and exit, their characteristics, and their integration into societies. These data need be comprehensive, accurate and frequently updated. There is no single source that can provide such data, but by combining several sources together it might be possible to produce the information that users need. Some countries have developed methods for combining administrative, statistical and other data sources for the production of migration statistics. This publication, developed by a task force of experts from national statistical offices and endorsed by the Conference of European Statisticians in June 2018, provides an overview of the ways in which data integration is used to produce migration statistics, based on a survey of migration data providers in over 50 countries. Thirteen case studies provide more detail on data integration in various national contexts. The publication proposes principles of best practice for integrating data to measure migration. The publication is designed to guide national statistical offices and other producers of migration statistics, while also offering users an insight into the production of the migration data they use.