This chapter presents information on the history, legislation and current approaches to assessing and controlling the potential hazards and risk of exposure to chemicals in the workplace. Historically, investigations of workplace exposures were post hoc, i.e. looking to identify the causes of diseases seen with increased prevalence in workers in particular sectors. The modern approach is to utilise data generated from in silico, in vitro and/or in vivo tests to set workplace exposure limits and control exposures such that they should not lead to any significant adverse effects. Exposure controls are mainly determined by limits, termed occupational exposure limits (OELs), based on airborne exposures. In the 1990s, there was a move to set OELs on a European Union (EU) basis with a harmonised value, rather than having individual Member States setting their own values for individual chemicals. The procedures for setting OELs adopted by the responsible EU body, the Scientific Committee on Occupational Exposure Limits (SCOEL), are described, including special considerations of carcinogens and mutagens, respiratory sensitisers, skin exposures, interactions with noise and the use of biological monitoring. Interactions with overlapping legislation such as classification and labelling and the setting of derived no effect levels (DNELs) under REACH (see also Chapter 10) are addressed. Challenges for the future of occupational toxicology and occupational hygiene include clearing the backlog of chemicals currently without a harmonised consideration of OELs and dealing with new forms of occupational exposures e.g. the expansion of technologies using nanoparticles.