The comparative study focuses on nine exploratory case studies of EU Member States: Austria, Belgium, Croatia, Germany, Italy, Romania, Slovakia, Slovenia, and Spain. The main research question for the individual country case studies was to see how the interplay of EU-regulation and national OSH systems affects the health and safety of posted workers in a transnational workplace. To answer this question, we looked into the way OSH regulation is applied to posted workers and their experiences with OSH-related issues, and at the legal and institutional framework on posting and OSH, cross-border communication and exchange, the mechanisms for grievances at different levels, the vulnerabilities of posted workers and language barriers.