1. Introduction. An overview. Computerization. 2. Gas Chromatography. Fundamentals. Van Deemter equation: significance, evaluation. Columns: packed columns, wall-coated open tubular columns. Detectors: thermal conductivity detector, flame ionization detector, electron capture detector. Analysis techniques: sample injection, temperature programming, retention index. Instrumentation: computerization, data acquisition and analysis. Suggested reading. 3. Mass Spectrometry. Fundamentals: electron ionization, chemical ionization. Instrumentation: quadrupole mass spectrometers, magnetic sector mass spectrometers. Interpretation of mass spectra: types of ions, isotopic abundances and characteristic ion clusters, nitrogen rule and rings-plus-double-bonds, steps in interpretation, examples, problems. Suggested reading. 4. Gas Chromatography-Mass Spectrometry. Vacuum and gas flow: basic principles, analysis of vacuum and gas flow, interfaces. Computerization: computerized operation, characteristics. Data analysis: reconstructed gas chromatogram, mass chromatogram, selected ion monitoring, background subtraction, Biller-Biemann stripping technique. Compound identification using reference spectra matching: mass spectral compilations, methods of computerized mass spectral search, commercial mass spectral computer search systems. Quantitative analysis by selected ion monitoring: choice of ions, magnetic versus quadrupole analyzers, identification and quantitation procedures, use of isotopically labelled compounds, precision, accuracy, and limit of detection. Automated GC-MS operation: automated data acquisition, automated data analysis, total automated analysis. GC-MS-computer instrumentation: Finnigan MAT systems, Hewlett-Packard systems. Suggested reading. 5. GC-MS-Computer Applications. Analysis of chlorinated dibenzo-p-dioxins and dibenzofurans: incinerator emissions, biological samples, summary and conclusions. Use of high performance liquid chromatography for complex mixture analysis: HPLC fractionation of the mixture into compound types. Use of high resolution GC-MS for identity confirmation. New developments: MS-MS: description of the technique, scan techniques, instrumental configurations, comparison of GC-MS and MS-MS. Suggested reading. 6. Glossary. Subject Index.