The National Institute for Occupational Safety and Health (NIOSH) is the Federal agency responsible for conducting research and making recommendations to prevent work-related injury, illness, and death. As such, NIOSH is active in (1) identifying critical issues related to possible health hazards of nanomaterials, (2) protecting the safety and health of workers involved in this emerging technology, and (3) implementing a strategic plan to develop and disseminate methods for safely advancing the technology through workplace controls and safe handling procedures, and (4) investigating the possible applications of nanotechnology to solve workplace safety and health issues. Because of their small size and large surface area, engineered nanoparticles may have chemical, physical, and biological properties distinctly different from larger particles of similar chemical composition. Those properties may include the ability to reach the gas exchange regions of the lung, travel from the lung throughout the body, penetrate dermal barriers, cross cell membranes, and interact at the molecular level. NIOSH is investigating all of these properties, as it would with any new technology or material in the workplace, to provide the necessary guidance to ensure a safe and healthy workplace.