Eighteen Chinese commercial brands of yogurt were collected from supermarkets from December 2002 to April 2003, for characterization of organochlorine pesticides (OCP) and polychlorinated biphenyls (PCB). Besides monitoring OCP and PCB by gas chromatography, the levels of extractable persistent organochlorine (EPOCl; i.e., sulfuric acid-resistant EPOCl) were also determined by instrumental neutron activation analysis. The results indicated that the contamination pattern of the selected OCP and PCB were in the order of dichlorodiphenyltrichloroethanes (DDT) approximately hexachlorocyclohexanes (HCH) >> aldrin > or = chlordanes > or = heptachlor epoxide and 4-6 chlorinated biphenyls (CB) >> 7-10 CB, respectively. Furthermore, beta-HCH, and 1,1-dichloro-2,2-bis (p-chlorophenyl) ethylene were the predominant isomers of HCH and DDT residues in yogurt, and PCB with 4,4'- and 2,3,5- substitution patterns were the predominant congeners of PCB residues. Also, the results indicated that the mean level of total chlorine in the identified organochlorine species was below 4% of EPOCl in yogurt, which implied that more than 96% of EPOCl measured in yogurt samples could not be accounted for by selected OCP and PCB.