1-Chloro-4-[2H]naphthalene was administered to a pig and the 4-chloronaphthol metabolite retained 18% of the deuterium. 1,4-Dichloro- and 1,4-dibromonaphthalene gave 2,4-dihalonaphthols as the major products and the results are consistent with the intermediacy of arene oxides; decomposition of these intermediates is accompanied by a 1,2 migration of deuterium and halogen, respectively. 1,2-Dichloronaphthalene and 1,2,3,4-tetrachloronaphthalene also give phenolic metabolites; however, the higher chlorinated isomer, 1,2,3,4,5,6-hexachloronaphthalene, was not metabolized. 1976, American Chemical Society. All rights reserved.