Constitutive models were developed and implemented numerically to account for the evolution of microstructure and anisotropy in finite-deformation processes involving porous and composite materials. Use was made of rigorous homogenization procedures developed by the PI under an earlier grant (AFOSR 89-0288). The constitutive models developed took a standard internal-variable form depending on suitably derived internal variables (serving to characterize the current state of the microstructure) and differential evolution laws for these variables. The main findings of the work are: (a) the evolution of the microstructure affects quite significantly the macroscopic response of porous materials; (b) there is synergistic coupling between the various microstructural variables, in particular, between the porosity and anisotropy; (c) qualitative agreement has been found with available experimental results, particularly for the non-uniform evolution of porosity and anisotropy in forming processes. The particular case of porous metals was considered in detail and the newly developed constitutive models were implemented in a general-purpose, finite-strain finite element program. Several problems in the area of metal forming were then analyzed, and implications for the onset of shear instabilities was explored.