The National Institute for Occupational Safety and Health (NIOSH) is pleased to present General Safe Practices for Working with Engineered Nanomaterials in Research Laboratories. Engineered nanomaterial applications are rapidly expanding throughout the United States and worldwide. The research community is at the front line of creating these new nanomaterials, testing their usefulness in a variety of applications, and determining their toxicological and environmental impacts. With the publication of this document, NIOSH hopes to raise awareness of the occupational safety and health practices that should be followed during the synthesis, characterization, and experimentation with engineered nanomaterials in a laboratory setting. The document contains recommendations on engineering controls and safe practices for handling engineered nanomaterials in laboratories and some pilot scale operations. This guidance was designed to be used in tandem with well-established practices and the laboratory's chemical hygiene plan. As our knowledge of nanotechnology increases, so too will our efforts to provide additional guidance materials for working safely with engineered nanomaterials.