This Practice Note examines the criteria that must be fulfilled in order for an individual to benefit from the protection of the Working Time Regulations 1998 (WTR 1998), SI 1998/1833. WTR 1998 applies to 'workers' and, under separate provisions, to agency workers. Separate provisions apply in relation to paid holiday for irregular hours and part-year workers. This Practice Note also outlines the exclusions and special provisions that apply in relation to: seafarers, workers where the characteristics of their work inevitably conflicts with the provisions of WTR 1998, young workers (under 18s), transport/mobile workers, trainee doctors, air transport (cabin crew) and domestic workers (ie servants in private households). Finally, it considers the application of WTR 1998 outside Great Britain. EU-derived laws such as WTR 1998, that have been made to implement UK obligations under EU law, are assimilated law. For further information, see Practice Note: Assimilated law. This Practice Note contains references to case law of the Court of Justice of the European Union (CJEU). For guidance on whether judgments of the CJEU are binding on UK courts,