In this study different multivariate methods were used to link the content of dioxins and furans in biota to different sources. The data used in the study were mainly from already existing analysis off dioxins and furans but also some data has been generated by sampling and analysis within the project. Lack of data, especially from biological samples, limited the modelling to the set of 17 toxic congeners comprised of seven dioxins and 10 furans. Two different multivariate modelling methods were used, principal component analysis (PCA) and positive matrix factorisation (PMF) for the source apportionment. The PCA shows that herrings from the Bothnian Bay and Gulf of Finland has well defined pattern. The spread in pattern is larger for the Herrings caught in The Baltic proper and Bothnian bay. Also the age of the Herring effect the patterns, 2-year old Herring are well grouped and separated from older Herrings. When adding source samples (flue gas, combustion, background) to the PCA for biota the only well defined overlap were between biota and flue gas. The PMF model for Baltic Herring points to three significant sources. One of them is identified to be a background/combustion. One of the other sources is not fully identified but some parts of the pattern are likely flue gas. The last source can not be identified by use of data collected in this project.