Fabric development and grain deformation behaviour in polycrystalline aggregrates involving one slip system have been numerically simulated. The model allows inhomogeneous deformation while still ensuring strain compatibility and overall stress equilibrium. Two types of inhomogeneous deformation occur in deformed polycrystals. Inter-grain strain inhomogeneity results from the contrasting deformability of neighbouring grains, which is dominantly determined by the corresponding initial slip-plane orientation. Intra-grain strain inhomogeneity arises because of the need to achieve strain compatibility across grain boundaries. Grain boundaries are generally the places where strain compromise is reached between neighbouring grains. Various microstructures are developed in deformed polycrystals. The development of kink-subgrain structures, a special type of subgrain observed in this model, is closely controlled by initial lattice orientation. The pattern of preferred orientations of slip planes is sensitive to strain history. In contrast, the preferred orientations of longer axes of deformed grains or passive plates in a deforming ductile medium are always parallel to the bulk extension direction, not showing any relevance to deformation history.