A constitutive equation for porous materials capable of supporting deviatoric stresses is described. The model incorporates the deviatoric stresses in a physically consistent manner so that the porosity is a function of the complete stress tensor and such phenomena as shear‐enhanced pore compaction may be represented. The constitutive equation is based on the physical concept of a closed yield surface in stress space which varies as the material porosity changes. An example of the application of the model to 22% porous 2024 aluminum is given.