The two stages of classical modelling (formulation of the governing equations and finding their solutions) become particularly difficult, in fact practically unfeasable, in the case of concentrated suspensions of long fibres in polymer melts. In such situations it may be useful to explore a completely different route. One such route is offered by the idea of direct simulations. On this route the model is formulated by specifying the fibre-solvent and the fibre-fibre interactions. The passage from the single-fibre point of view to the macroscopic view on which rheological properties and the microstructure are observed is made by first calculating trajectories of all fibres in a model-system composed of several hundreds of fibres and making appropriate averages. The preliminary results of such simulations are in a good qualitative agreement with experimental observations for. polypropylene melt reinforced by long glass fibres. For examples, dilution and migration of fibres away from die walls are predicted; it is also observed that in concentrated situations the fibres form bundles which could in the entry flow generate large energy dissipation and oscillations.