This presentation deals with an investigation of the mechanisms that govern the long-range transport of persistent organic pollutants (POPs) in the environment.  Two multimedia box models of the global system are used in the investigation. ChemRange is a purely evaluative, one-dimensional steady-state model and CliMoChem is a two-dimensional model with different temperatures, land-water ratios and vegetation types in different latitudinal zones. Model results are presented for four case studies: (i) the effect of atmospheric aerosol particles on the long-range transport of POPs, (ii) the effect of export to the deep sea on the long-range transport of different PCB congeners, (iii) the global fractionation of different PCB congeners, and (iv) the influence of vegetation on the distribution dynamics of POPs. The model results show that the long-range transport of POPs is the result of the interaction of many, often counteracting processes. The models prove useful as analytical tools for identifying these processes and their importance. Important research needs concern the physicochemical properties and the environmental degradation rate constants of semivolatile organic chemicals.