It is generally recognized that trace analysis implies those analyses that are carried out around 0.0001% or ppm level. Ultratrace analysis, ie, what is ordinarily beyond what is called trace analysis, can be then defined as analysis performed below ppm or μg/g level. Residue analysis relates to the analysis of residual materials left from an operation, eg, solvents left in pharmaceutical products or pesticides left in food. Analyses performed at or below ppm level are described. Sampling, sample preparation, sample cleanup, and sample validation are discussed. A number of methods are covered such as atomic absoprtion/emission spectrometry, neutron activation analysis, tlc, gc, hplc, hyphenated methods such as gc/ms and lc/ms, capillary electrophoresis, supercritical fluid chromatography, and immunoassays that allow analysis of both organic and inorganic samples. Applications areas include for example, the environment, explosives, food, pharmaceuticals, and biotechnology,