One of the deliverables in large scale assessments (LSAs) is a database which is frequently publicly accessible for further research and analyses. In this chapter, Alla Berezner and Eveline Gebhardt describe procedures and issues related to the construction of a database which is challenging given the complex sampling procedures and rotated booklet design used to collect data from thousands of students, their parents, teachers and schools. The issues discussed relate not only to the database itself but also to its documentation, for example, through compendia which include a set of tables showing descriptive statistics for every item in the cognitive tests and the questionnaires or through encyclopaedias which provide information about the participating education systems. Finally, the chapter discusses that databases need to be accompanied by user guides aimed at providing information for the appropriate use of the data in subsequent analyses which, in turn, are often supported by hands‐on training of analysts who use these databases.