The mechanical behavior of microporous polyurethane foams used in poromeric materials can be described by use of a model comprising of struts of square cross section arranged in a cubical lattice. The model was initially proposed by Gent and Thomas to describe the properties exhibited by natural rubber latex foams. The microporous polyurethane foams used in poromerics are in general much stronger than natural rubber foams, and it has been found that their tear and tensile properties are dependent on the size of the largest pore, which can be up to 20 times greater in diameter than the average pore size. The behavior of the polyurethane foam in compression can be satisfactorily described by use of this cubical model and shape factor theories from polymer engineering.