This is version 4.0 of the ‘Requirements for certification of data centres’, published by ECRIN, the European Clinical Research Infrastructure Network (the first version was produced in 2011, the second in 2012, and the third in 2015). The requirements are the criteria used by ECRIN to identify, and then certify, clinical trials units that can provide high quality, compliant and safe data management, as well as effective management of the underlying systems and IT infrastructure. This latest version results from a review in 2017 and 2018 by ECRIN auditors, members of ECRIN’s data centre Certification Board, and invited experts from a variety of trials units in Europe. The full list of contributors is provided on page iv. Over and above their use for certification, the requirements are intended to describe good practice in data and IT management in clinical research, and in clinical trials in particular. They were developed by senior staff working in non-commercial clinical trials units in Europe, and are intended as a practical guide for staff working in IT and data management in that sector (though the same principles apply to all clinical research environments). The 106 requirements, or standards, included in the current version are divided into 16 separate lists, some focused on IT, some mainly concerned with data management, and some that deal with more generic aspects of trial management. Each standard has a code, a title, and a single statement summarizing the requirement. This document provides, in addition, explanatory and elaboration material that attempts to clarify each statement’s meaning, and / or give examples of its application, and which also indicates the evidence that would normally be used to assess a unit’s compliance. The document also includes a brief introduction to the standards and their development, including a description of the ECRIN Data Centres audit process, a glossary of terms, and a summary of the main changes from the previous version.