A comparative metabolism of [benzyl 14C]deltamethrin and 3-phenoxybenzoic acid (3-PBacid) was carried out in chickens. The effect of oral and intravenous route of administration was also investigated. There was no difference in the metabolic profile of [14C] portion of deltamethrin and 3-PBacid. Similarly, no effect on the nature of metabolites excreted due to mode of administration was observed. Biotransformation of orally dosed compounds did not occur in the intestine, but were absorbed and metabolized by liver (deltamethrin) and kidney (3-PBacid). 3-PBacid, the primary metabolite of deltamethrin, was readily metabolized into 3-hydroxy benzoic acid (3-HO-Bacid) which is conjugated with a variety of endogenous substances to form sulphates, glucuronides, butyl ester and peptides. HPLC and LC-Ms methods were used to ascertain the structures of metabolites.