Sintering of powder metal compacts is one of the basic oper- ations in powder metallurgy. The useful properties of a machine part are obtained after considerable densification of the sintered material. Although the mechanical properties of the part depend on other structural factors besides porosity, porosity is the main factor. Usually, the practical problem in sintering is to obtain a part with the desired or permissible porosity. Thus, knowledge of the laws governing densification and its final result is neces- sary to control this process in the production of powder metal parts. The laws governing densification are also important for a more exact physical theory of sintering, which is still in the initial stages of its development. Such processes as the change in the density of lattice defects and the flow of crystalline substances during sintering have not yet received a complete physical inter- pretation. Analysis of the laws of sintering may provide addition- al material for more complete phenomenological characteristics of these processes that will be useful for further development of theoretical concepts of the flow of imperfect crystals under small loads. Although a substantial amount of experimental material has been accumulated, generalizations are still difficult.