1. Absolute and relative energy absorptions during the pressing of powders are related to deformation rate by a logarithmic law. 2. The magnitude of energy absorption may be expressed by an equation consisting of two terms. The first term represents an increase in absorption with increasing degree of deformation, and the second a drop in absorption with increasing deformation time. 3. Both relative absorption and differential relative absorption are sensitive characteristics of the properties of materials undergoing deformation. This is evident in the case of iron, where the unstable deformation process in the zone of yield strength is quite clearly reflected in instability of relative energy absorption in the same region. 4. The maximum relative absorption corresponds to the beginning of plastic deformation of particles. The relative absorption of energy in this region attains 84%, indicating that practically the whole work of deformation is absorbed by the lattice, and only a small proportion of it is evolved in the form of heat.