In many fields, nanotechnology is leading to the development of purposely-engineered nanoparticles and devices demonstrating new, unique and non-scalable properties. However, concern has been expressed that these same properties may present unique challenges in terms of the potential health impact. Airborne particles associated with engineered nanoparticles are of particular concern, as they can readily enter the body through inhalation. Research into the potential occupational health risks associated with inhaling engineered nanoparticles is actively being conducted in the U.S. and globally. In this article, the potential occupational health effects of inhaled nanoparticles and methods for measuring exposure to nanoparticles are discussed. Critical research needs in this field are also briefly addressed.