The effect of a rubber mould on densification and deformation of aluminum alloy powder was investigated during warm isostatic pressing. The hyperelastic constitutive equations based on various strain energy potentials were employed to analyze deformation of a rubber mould. The parameters in the strain energy potentials were obtained from experimental data for uniaxial and volumetric responses of Viton rubber at elevated temperatures. The yield function of Shima and Oyane was implemented into a finite element program (ABAQUS) to predict compaction responses of metal powder during warm isostatic pressing. Finite element results were compared with experimental data for densification and deformation of aluminum alloy powder during warm die pressing and warm isostatic pressing. (C) 2004 Elsevier B.V. All rights reserved.