The structural characteristics for particular automotive structural components are systematically related to representative, typical structural design criteria and design constraints for a production vehicle. Based on these relationships, we establish the structural design requirements to be satisfied when a substitute material is used in an automotive structure.A simplified method is developed for evaluating the desirability of directly substituting materials to reduce the weight of automotive structures. This is done by explicitly relating the change in weight to the corresponding changes in structural characteristics, when a specific mild steel structure is “replaced” by one differing only in material and gage. By means of this method, material trade-offs can be directly evaluated by engineers and designers early in the design stage. Examples are given for aluminum and high-strength steel as candidate substitutes for mild steel.