This report considers the sources of environmental contamination from biphenyl and diphenyl oxide. Biphenyl is manufactured in commercial quantities for use in dye carriers, heat transfer fluids, derivatives such as PCB's and alkylated biphenyls, and fruit fungicides. Diphenyl oxide is manufactured in commercial quantities for use in dye carriers, heat transfer fluids, derivatives such as butylchlorodiphenyl oxide, decabromodiphenyl oxide, surfactants, and perfumes and soaps. Thus, this report concentrates on the commercial production and use of biphenyl and diphenyl oxide. Standards established by the Occupational Safety and Health Administration have controlled the occupational exposure to biphenyl and diphenyl oxide; however, large quantities of these chemicals are released to the external environment, particularly to waste treatment facilities which may utilize chlorine disinfection. Laboratory studies indicate that the biphenyl nucleus can undergo chlorination to various chlorobiphenyl isomers during treatment chlorine disinfection.