The synthesis of all possible Isomeric nona- and octachlorobiphenyls has been accomplished by the Cadogan coupling of commercially available or synthetic chlorinated anilines in the presence of excess chlorinated benzenes and isoamyl nitrite. 2, 3, 4, 6-Tetrachloraniline was prepared by the chlorination of 2, 4, 5-trichloroaniline. The synthetic polychlorinated biphenyls (PCBs) were characterized by their proton magnetic resonance and mass spectra and their purities determined by gas chromatographic analyses. The PCB standards were used to unambiguously identify the deca-, nona-, and octachlorobiphenyls present in human breast milk and in the commercial PCB preparations Arociors 1268, 1262, 1260, 1254, 1248, 1242, 1016, 1232 and 1221 utilizing high resolution glass capillary gas chromatography.