Throughout this work PBDEs level determination in biota was developed for the first time in Portugal. The data obtained was important to provide a global perspective of Portugal contamination by PBDEs and allows the comparison with studies made in other countries. Environmental levels of fourteen polybrominated diphenyl ethers (PBDEs) were analysed in a number of biota samples (Barbus sp. and Mytilus galloprovincialis) taken over a large geographic range covering five rivers and coastal areas of Portugal. Tetrabromodiphenyl ether (BDE 47) was found in almost all samples ranging from not detected (nd) to 30ngg(-1) dry weight (dw). BDE 47 concentration is correlated with mussels weight indicating the bioaccumulation of this compound. Pentabromodiphenyl ethers (BDE 99 and BDE 100) were detected in several samples, but in lower concentrations.