Abstract: As an initial attempt to set up a "Freshwater Mussel Watching" system,swan mussels(Anodonta woodiana) were collected from Wuli Lake of the Taihu Lake in March 2003 for analysis by gas chromatography of dichlorodiphenyltrichloroethanes(DDT)(p,p′-DDE,o,p′-DDT,p,p′-DDD,p,p′-DDT),and α-,β-,γ-,δ-hexachlorocyclohexane (HCH) isomers in soft tissues.Except for β-HCH isomer,all DDT and HCH isomers were detected in these mussels.ΣDDTs concentration range: 5.86～14.13 ng·g^-1 wet weight,mean±S.D.:(9.27±3.04) ng·g^-1 wet weight,n=10 were higher than ΣHCHs concentration range: 2.45～6.46 ng·g^-1 wet weight,mean±S.D.:(4.00±1.22) ng·g^-1 wet weight,n=10.The former was dominated with p,p′-DDE,p,p′-DDD,while the latter with α-,γ-HCH,suggesting that recently input of DDT was getting little, but the input of HCH was apparent in the region.However,DDT and HCH residues in the mussel samples were still lower than the threshold values set by the Ministry of Agriculture of China,as well as FDA and FAO.