The NIOSH Pocket Guide to chemical hazards is presented. The guide contains information taken in part from NIOSH or OSHA occupational health guidelines for chemical hazards. Data was also obtained from recognized text books in the fields of industrial hygiene, medicine, toxicology, and analytical chemistry, and articles from a variety of technical journals. The guide was developed as a means for making information contained in the NIOSH or OSHA guidelines more conveniently available to workers, employers, and occupational health professionals. It presents key information and data in an abbreviated tabular format for 397 individual chemicals or chemical types found in the work environment and for which there are specific Federal regulations. Information contained in the guide includes: chemical names and synonyms, exposure limits and recommendations, chemical and physical properties, analytical methods, respirator and personal protective equipment recommendations, signs and symptoms of exposure, and procedures for emergency treatment. It is noted that implementing the industrial hygiene and medical surveillance practices recommended in the guide will assist in initiating and maintaining effective occupational health programs.