Several individual and multiresidue analytical methods are available for gas chromatographic-mass spectrometric confirmation and identification of pesticide residues. Specific examples considered in this report include the analysis of intact and derivatized phenolic residues such as pentachlorophenol and 1-naphthyl chloroacetate, organophosphorus insecticide metabolic and hydrolytic products including O,O-diethyl O-methyl phosphorothionate, O,O-diethyl S-methyl phosphorothiolate, and O,O-diethyl O-methyl phosphate, several organochlorine pesticides of the DDT and cyclodiene type, phenoxyalkanoic acid herbicide exposure and methodology studies involving 2,4-D and 2,4,5-T, and polychlorinated biphenyl residues. Conventional residue analytical methodology and gas chromatographic column technology are, in general, directly applicable to the analysis of human, animal, and environmental substrates by the combined technique. Evaluation of mass spectral fragmentation pathways provides definite and conclusive confirmation of residue identity as well as characterization of residues and their metabolites of unknown structure.