Grain subdivision during cold deformation of pure f.c.c. metals is modelled with the help of a coupled substructure-texture evolution algorithm. The substructure is assumed to consist of non-misoriented, microscopic cells and of misoriented, mesoscopic fragments. The cell walls are represented in terms of redundant dislocation densities. The fragment boundaries are assumed to develop in a "nucleation and growth" process along the cell walls and are represented in terms of non-redundant dislocation densities. The substructure development is modelled by rate equations for dislocation and disclination densities in six cell wall and fragment boundary families. All the rate equations are driven by slip rates as calculated from a Taylor FC texture model. Starting from a critical misorientation, the fragments are treated as independent texture elements. For standard rolling texture components, cell and fragment sizes as well as fragment misorientations can be predicted in good agreement with experimental results.