Stack‐collected fly‐ash particles from a commercial pulverized‐coal power plant were extracted with 60/40 w/w benzene‐methanol to remove as much of the organic fraction as possible. The extract was sequentially fractionated on a series of high‐performance liquid chromatography columns, and the Salmonella bacterial mutagenicity assay using both normal and nitroreductase‐deficient strains was used to localize the most mutagenic fractions. Selected fractions were analyzed by a variety of techniques, including gas chromatography with dual‐flame ionization and thermionic nitrogen‐phosphorus detectors, gas chromatography‐mass spectrometry, directprobe low‐resolution or low‐voltage mass spectrometry, and high‐resolution mass spectrometry.