An adequate physical and mathematical description of material be­ havior is basic to all engineering applications. Fortunately, many prob­ lems may be treated entirely within the framework of elastic material response. While even these problems may become yuite complex be­ cause of geometrical and loading conditions, the linearity, reversibility, and rate independence generally applicable to elastic material descrip­ tion certainly eases the task of the analyst. Today, however, we are in­ creasingly confronted with practical problems which involve material response which is inelastic, hysteretic and rate dependent combined with loading which is transient in nature. These problems include, for instance, structural response to moving or impulsive loads, all the areas of ballistics (internal, external and terminal), contact stresses under high speed bearings, high speed machining, rolling and other metal working processes, explosive and impact forming, shock attenuation structures, seismic wave propagation, and many others of equal im­ portance. As these problems were encountered, it became increasingly evident that we did not have at hand the physical or mathematical description of the behavior of materials necessary to produce realistic solutions. Thus, during the last ten years particularly, there has been considerable effort expended toward the generation of both experi­ mental data on the dynamic mechanical response of materials as well as the formulation of realistic constitutive theories. It was the purpose of the Symposium at which the articles in this book were presented to discuss and review recent developments in this field.