This supplement to the NIOSH Manual of Analytical Methods contains twenty new methods, (aerobic bacteria (0801); alachlor in air (5603); aniline, o-toluidine, nitrobenzene (2017); benzene soluble fraction & total particulate (asphalt fume) (5042); benzothiazole in asphalt fume (2550); bioaerosol sampling (0800); formaldehyde (DNPH) (2016); chlorinated and organonitrogen herbicides (air sampling) (5602); chlorinated and organonitrogen herbicides (patch) (9201); chlorinated and organonitrogen herbicides (hand wash) (9200); lead (port XRF) (7702); lead by ultrasound/ASF (7701); n-methyl-2-pyrrolidone (1302); mycobacterium tuberculosis, airborne (PCR) (0900); nicotine (2551); organonitrogen pesticides (5601); perchloroethylene (portable GC) (3704); polycyclic aromatic compounds (5800); recorcinol (5701); p-toluenesulfonic acid (5043);), eleven revised methods, (acetonitrile (1606); elemental carbon (5040); isocyanates (5522); methanol (2000); methylene chloride (1005); nitroaromatic compounds (2005); nitrogen dioxide (diffusive sampling) (6700); particulates, respirable (0600); polynuclear aromatic hydrocarbons (5506); silica, chrystalline (7500); vinyl acetate (1453);), and twelve corrected methods, (n-butyl mercaptan (2525); cobalt and compounds, as Co (7027); elements by ICP (7300); epichlorhydrin (1010); ethylene oxide (1614); fluorides by IC (7906); glutaraldehyde by HPLC/UV (2532); glycols (5523); lead by flame AAS (7082); lead GFAAS (7105); phosphine (6002); toluene (diffusive sampline) (4000);), and one new chapter. The method finder, contents, and indexes have also been updated to coincide with the changes. The replacement pages are included. The manual is a collection of air, biological, bioaerosol, and bulk analytical methods that NIOSH has evaluated. NMAM will be updated as methods are developed, evaluated or revised by NIOSH. These methods are intended to promote accuracy, sensitivity, and specificity in industrial hygiene analyses. The introduction states the purpose and use of the manual. Subsequent sections discuss the quality assurance, sampling, measurements, methods, standards, blanks, blind samples, recovery studies, duplicates, tracking, and reporting. In addition, information to be considered when sampling for airborne contaminants; types and uses of solid sorbents; factors affecting the collection of gases, vapors, and aerosols; sampling strategy and calibration techniques; and samplers is presented.