Criteria and recommended standards for cotton dust exposure are reported, as developed by the National Institute for Occupational Safety and Health (NIOSH). The Occupational Safety and Health Act of 1970 emphasizes the need for standards to protect the health and safety of workers exposed to an ever-increasing number of potential hazards at their workplace. NIOSH has projected a formal system of research, with priorities determined on the basis of specified indices, to provide relevant data from which valid criteria for effective standards can be derived. Recommended standards for occupational exposure, which are the result of the current study, are based on the health effects of exposure. It is intended to present successive reports as research and epidemiological studies are completed and sampling and analytical methods are developed. Criteria and standards will be reveiwed periodically to ensure continuing protection of the worker. Seven review committees are outlined that were established to make recommendations regarding a cotton dust standard. The biological effects of exposure are discussed and environmental sampling data are reported. The basis for the recommended environmental standard on cotton dust is presented and work practices for protection are described.