The current state of backscatter modelling of forested regions is reviewed, with a view to outlining possible future developments if suitable models are to be available to support research with forthcoming multi-waveband, multi-polarization radar sensors. By decomposing the physical structure of the forest into identifiable units, appropriate scattering expressions for each of those physical components are summarized. Particular attention is paid to pairwise interaction mechanisms involving two components (trunk-ground interaction is an example), since these can give rise to higher scattering levels than individual scattering events. It is suggested that further attention must be given to interaction mechanisms, especially in complex forest structures. © 1990 Taylor & Francis Ltd.