The concentrations of hexachlorocyclohexanes(HCHs)in the sediment cores taken from the Dongtan Wetland at the Yangtze River Estuary of the East China Sea were measured by isotope dilution mass spectrometry (IDMS)with HRGCHRMS. The vertical distribution characteristics of HCHs concentrations with depth and possible influence by climate changes were preliminarily discussed.HCHs were found in all sediment layers.The total HCHs concentrations range from 0.35to 0. 98ng·g~(-1)dw with the average of 0.64ng·g~(-1)dw for the Dongtan Wetland,showing a low pollution level.The vertical distributions of HCHs isomers in the cores showed significant periodic variations.By time-series analysis,the long-term variation trends and frequency spectra of HCHs in the sediment cores of the Dongtan Wetland during the last 60years were discussed. The long-term variation trends of HCHs in the wetland showed that these chemicals began to rise in the early 1950swith the maxima during the 1960s~1970s.Some isomers did not show significant declining trends after their productions were banned. The time-series generally show an 8-year periodicity,suggesting an influence of ENSO.