The neurobehavioral testing and research programs of NIOSH, established under the Department of Health, Education, and Welfare, were reviewed. Human neurotoxicity testing was emphasized. NIOSH sponsored neurobehavioral research included animal and human testing in the laboratory and on site observations of workers. Two types of field investigations were identified. These included health hazard evaluations and industry wide studies. The hazard evaluations were done in response to specific assessment requests evolved from workers, management, or organizations within a company. Information in the health hazard evaluation report included measured levels of exposure to toxic substances, site medical records, clinical test results on workers, and recommendations for improved engineering controls and work practices. Industry wide studies were directed towards an entire industry, work process, or specific chemical or group of chemicals and resulted from a need to provide information in response to specific research questions. Laboratory studies using human subjects were directed toward determining neurobehavioral function during carefully monitored inhalation exposures to chemicals at concentrations below the permissible exposure levels established by the Occupational Safety and Health Administration.