A supplement to the December issue of the Journal of Occupational and Environmental Hygiene (JOEH), will address current issues related to the science of setting occupational exposure limits (OELs). The ten articles in State of the Science of Occupational Exposure Limit Methods and Guidance resulted from collaborations between scientists at the National Institute for Occupational Safety and Health (NIOSH), Toxicology Excellence for Risk Assessment (TERA), and other organizations.