Comparative temporal trend studies of ΣDDT and PCB on the Baltic pollution, using matrices from Baltic biota and dated lamina from sediment cores in anoxic sediment areas of the Baltic (no bioturbation) have been carried out. Chemical analyses of consecutive laminas of the cores representing individual years were compared to long-term temporal trend monitoring of Baltic biota based on annual sampling and analyses. Earlier studies of sediment cores from the Baltic have often indicated increasing concentrations of halogenated organic compounds in recent time whereas monitoring of Baltic biota showed decreasing concentrations from the 1970s and onwards. In the present study two sediment cores from the northwestern Baltic proper indicate a concentration (dry weight basis) peak in the same time period as for biota, but the decrease during recent decades is slower than for biota. In lamina representing the period 1940–1950 remarkably high concentrations of both PCB and ΣDDT were found. Interestingly also a high proportion of nonmetabolized DDT was found in these old lamina, whereas lamina representing 1960–1970 showed a low portion of nonmetabolized DDT and high portions of the metabolites DDE and DDD during the period 1970–1998. The results are discussed in relation to resuspension of sediments, diffusion and interstitial transport of halogenated organic compounds in the sediment cores. The results indicate the importance of resuspension of sediment and that carbon normalized data are inappropriate for interpretation of temporal trends. The results also show that we have no appropriate model to interpret the pollution of the Baltic by halogenated organic compounds, retrospectively, by using lamina from anoxic sediment cores, but that we urgently need more knowledge on the important retention mechanisms in sediment.