A variety of chlorinatedp-terphenyls was photolyzed in organic media at 300 nm. Replacement of chlorine by hydrogen (dechlorination) was the major reaction. Substitution products were much more prominent than in the corresponding reactions of polychlorinated biphenyls.Quantum yields of reaction were substantially higher forortho-chlorinated compounds. Xenon-assisted reactions and benzophenone sensitization indicate a triplet reactive state, although energy transfer from benzophenone is very inefficient. Triethylamine promoted an electron transfer pathway but only for those compounds that were least photolabile.