More and more Member States require immigrants from outside the EU to pass language or knowledge-of-society tests in different stages of the immigration and integration process. This article focuses on the application of this requirement as a condition for obtaining a permanent residence permit or the EU long-term resident status. It is based on an international comparative study that included seven Member States with integration conditions (Austria, Denmark, France, Germany, Latvia, the Netherlands and the United Kingdom). The article analyses the reasons behind the introduction of language and knowledge tests for applicants for a permanent residence permit or the EU long-term resident status in these Member States. Secondly, it examines the effects of the tests on the integration process of third-country nationals admitted for non-temporary stay. Finally, it discusses the legal constraints posed by EU and international law.