Polybrominated diphenyl ethers (PBDEs) have been intensively used as flame retardants (FRs) and have become ubiquitous environmental pollutants. PBDEs form hydroxylated PBDEs (OH-PBDEs) as metabolites. Further, some OH-PBDEs and methoxy-PBDEs (MeO-PBDEs) are natural products. These are all compounds of environmental and health concern and it is therefore important to confirm their identity and to assess their environmental levels and toxicities. Hence, it is vital to obtain authentic reference standards of individual PBDEs and OH/MeO-PBDEs. The thesis main aim was to develop synthesis methods of congener specific PBDEs, OH- and MeO-PBDEs. The second aim was to identify and quantify PBDEs, OH- and MeO-PBDEs in environmental samples. The third was to propose an abbreviation system for FRs. O-Arylation of brominated phenols, using either symmetrical or unsymmetrical brominated diphenyliodonium salts, was selected for synthesis of PBDEs and OH-/MeO-PBDEs. A total of 16 MeO-PBDEs, 11 OH-PBDEs, 1 diMeO-PBDE and 1 EtO-MeO-PBDE were synthesised. Three novel unsymmetrical diaryliodonium triflates were synthesised and used in synthesis. Optimisations were made to construct a reliable general method for congener specific PBDE synthesis, which was used in the synthesis of 8 representative PBDE congeners. The products were generally characterised by electron ionisation mass spectrometry (EIMS) and nuclear magnetic resonance (NMR) spectroscopy. Identification of PBDEs and OH-PBDEs in various matrixes was based on gas chromatographic and mass spectrometric analyses. Fourteen OH-PBDE congeners were identified in a pooled human blood sample. One previously uncharacterised natural PBDE analogue was identified as 6-OH-6’-MeO-BDE-194, and quantified in Swedish blue mussels. PBDE congeners and other BFRs were identified and quantified in workers and dust from a smelter in Sweden. A structured and practical abbreviation system was developed for halogen- and phosphorus containing FRs. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Submitted. Paper 4: Manuscript.</p>