The energy absorbed during the axial collapse of a variety of structures made in steel, aluminum alloy and glass fiber reinforced plastic is examined with respect to the changes produced by foam filling. A simple-model is devised which permits reasonable estimates of the axial collapse load for a structure and an assessment of the weight effectiveness of foam filling for that structure. Design charts are given, from which the dimensions can be derived for sections made in either steel or aluminum alloys of any particular strength level, in order to establish the weight effectiveness of foam filling. On a weight effectiveness basis, foam filling is primarily of value only in sections made from high density, low strength materials, e.g., mild steel. For mild steel foam filling becomes weight effective in sections having a thickness: section side ratio of less than .02 approximately. In the case of brittle materials, e.g., fiber reinforced plastics, foam filling promotes the crush stability of the structure. Such improvements in this stability may be the major need for foam filling in these sections and also in large, thin-wall metal sections.