It is now well established that severe plastic deformation (SPD) leads to a very significant reduction in the grain size of many metallic materials. Processing by SPD may be achieved through torsional straining by rotating a disk around its center or by rotating a cylindrical rod about its longitudinal axis. High-Pressure Torsion (HPT) is a typical torsional straining procedure which may be used to produce an array of ultrafine grains having average sizes lying in the submicrometer or the nanometer range. Generally, the HPT process is applied to disk samples but very recent studies have demonstrated that HPT is applicable also to bulk samples. The principle of torsional straining was also recently developed as a Severe Torsion Straining Process (STSP) in which a rod is moved in a longitudinal direction while torsional strain is introduced through rotation. This report describes both the principles and some typical results attained using these various torsional straining procedures.