Some polychlorinated diphenyl sulfides were prepared by chlorination of diphenyl sulfide with sulfuryl chloride and by Friedel-Crafts-type reaction from 1,2-dichlorobenzene and sulfur. Individual isomers from the reaction mixtures were isolated by reversed-phase high-performance liquid chromatography. Mass spectra show the degree of chlorination of different compounds, and H-1 and C-13 NMR spectra verify their structures. Three trichloro isomers were shown to be 2,2',4-,2,4,4'-, and 2,4',6-trichlorodiphenyl sulfides and two symmetric tetrachloro isomers bis(2,4-dichlorophenyl) and bis(3,4-dichlorophenyl) sulfides. Chlorine-induced C-13 NMR substituent chemical shifts (SCS) have been calculated and compared with the experimental ones in the case of bis(2,4-dichlorophenyl) sulfide. Four stack gases from a waste incinerator and six pulp mill effluents from two bleaching plants were screened for the polychlorinated diphenyl sulfides. Trichlorodiphenyl sulfides were found from five pulp mill effluent samples and tri- and tetrachlorodiphenyl sulfides from two stack gas samples.