This paper is concerned with the mechanical property changes in drawing/extrusion operations of hardening viscoplastic materials with damage. The process model in this study includes two state variables, the hardness for strain hardening from slip dominated plastic distortion and the porosity for damage from growth of microvoids. The decrease in apparent density in strip drawing of aluminum for several die angles are computed and compared with that from experiments. Simulations of axisymmetric drawing/extrusion have shown that the accumulated porosity in drawing is much bigger than that in extrusion while the difference between the hardness distributions in these processes are insignificant. The effects of the process conditions, such as conical die angle, friction and drawing/extrusion speed, on the mechanical property changes are also examined.