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The occurrence of volatile halogenated compounds in spent liquors from kraft softwood and hardwood pulp bleaching processes was studied. The identity of the low-molecular-mass constituents was verified by capillary gas chromatography—mass spectrometry using an NBS/Wiley reference database and mass spectra of reference compounds. The purgeable fraction of the first chlorination stage of the softwood pulp contained numerically most of the organohalogen compounds detected. The ratio of chlorine to chlorine dioxide applied at this stage greatly affected the formation of the compounds. Identity was confirmed for fourteen components, of which two, dichloroacetonitrile and trichloromethanesulphonyl chloride, have not been previously identified in, e.g., bleach kraft effluents. The most abundant volatile compounds were chloroform, 1,1,1-trichloropropanone, trichloromethanesulphonyl chloride, 1,1,2,3,3-pentachloro-1-propene and pentachloropropanone. Several of these volatile compounds are known mutagens or suspected carcinogens.