The European Working Time Directive lays down minimum safety and health requirements for the organisation of working time in the EU by, for example, establishing that all workers have the right to a limit to weekly working time of 48 hours. However, it also contains the possibility for Member States to allow for the opting out of that maximum as long as the individual workers agree. This report looks at how the Member States make use of the possibility of opting out, the extent of its use and its main impacts. Although national data about its use are scarce, the opt-out and long working hours continue to be the subject of heated debates involving governments and social partners across the EU. According to the research currently available, there are strong reasons to think that the limitation of working time is beneficial for everyone, including workers, employers, patients and clients.