In this working paper, Jan Cremers describes the situation of third-country nationals in the EU labour market. What do we know about their conditions of entry to the labour market, employment and integration into the posting of workers scheme? What is the legal framework governing the labour relationship and access to social security coverage? What difficulties are encountered in enforcing their rights? While the situation of third-country workers is the result of a delicate combination of national and European rules governing immigration control, access to the labour market and law enforcement, this document suggests a number of ways of improving the effectiveness of their rights. The synthesis of the collection of practices carried out for the Eurodétachement- ED6 project on this issue is appended to the document.