The objective of this paper is to present recent modifications to the Bodner-Partom viscoplastic equations for improved prediction of strain rate and temperature effects on the plastic flow behavior of metals. The thermal softening and strain hardening characteristics widely differ from metal to metal. For example, experimental results using the Kolsky apparatus (split Hopkinson bar) show that the shapes of flow stress vs. temperature curves substantially differ between aluminum and copper. A recent modification of the Bodner-Partom model accounts for strain rate dependence of hardening. By describing the saturated value of hardening, Z1, as a function of temperature, plastic flow behavior in copper has been successfully modeled.