A new method was developed for determining the dynamic stress-strain relationships of materials subjected to high rate of torsional loading. In addition, an investigation of propagation of torsional plastic waves in a long tube was conducted. Commercially pure copper was used throughout both investigations. In the material property studies, shear strains up to 20 percent and shear strain rates to 2100/sec were obtained. The results indicated that copper exhibits significantly lower strain-rate effects than those previously obtained by the longitudinal loading method. In the studies of plastic wave propagation, shear strain-time records at several cross sections along the tube were compared with computed results obtained from the strain-rate-independent and strain-rate-dependent theories. It is concluded that the computed results based on the strain-rate-dependent theory give better agreement with the experiments.