The results are presented of experimental examination of time effects in loading and unloading at moderately high rates light alloys (VT1-1 titanium and D16 aluminum alloy) characterized by typical rheonomical and scleronomical properties. It is shown that the dynamic yield limit in unloading may greatly exceed the static yield limit. Consequently, the extensively used unloading hypothesis proposed by Malvern appears to be incorrect. Attention is given to problems in simultaneous description of both active and passive processes using certain widely used relations of dynamic ductility. The resultant experimental data can be successfully analyzed using the variant of the endochronic theory of viscoplasticity in which no difference is made between the active and passive processes.