A global multimedia model is used to calculate the fate of polybrominated diphenyl ethers (PBDEs) in the environment. Special emphasis is given to the importance of direct photolysis, which has been shown to be an important degradation mechanism for highly brominated PBDEs and is believed to result in the formation of lower-brominated PBDEs. We show that the inclusion of direct photolysis decreases the overall persistence and long-range transport potential of most PBDEs, in particular the heavier ones. We develop a PBDE emission inventory and calculate environmental concentrations of different PBDEs. Differences between predicted concentrations and field data are assessed and possible reasons for these differences discussed. The formation of lighter PBDEs by debromination of deca-BDE is compared to direct emissions of lighter PBDE homologues. The model estimates that about 13% of the penta-BDE and about 2% of the tetra-BDE homologue found in the environment arise from the degradation of deca-BDE. Uncertainties of the model estimates are quantified and their implications for the findings of our study discussed.