This supplement contained 34 methods of analysis for 69 toxic chemical compounds and served as an update to the NIOSH manual of analytical methods. Methods were selected on the basis of their use, input from the clients and NIOSH chemists on need for change, and the health implications of the compounds. Methods were included for acetaldehyde (75070), acetic-acid (64197), acrylonitrile (107131), aldehydes, aliphatic amines, aminoethanol compounds, asbestos (1332214) bulk and fibers, 1-butanethiol (109795), chlordane (57749), hexavalent chromium compounds, cyanuric-acid, (108805), ethyleneamines, endrin (72208), fibers, formaldehyde (50000), furfuryl-alcohol (98000), glutaraldehyde (111308), hydrogen-cyanide (74908), isocyanates, ketones, mercury (7439976), methyl-methacrylate (80626), nitrosamines, pentachlorophenol (87865), quartz (14808607) in coal mine dust, ribavirin (36791045), respirable crystalline silica, sulfur-dioxide (7446095), toluene diamines, and valeraldehyde (110623).