Severe plastic deformation is characterized by the intense strain hardening and low efficiency of dislocation mechanisms of deformation (through a noncorrelated motion of dislocations). For this reason the processes of plastic flow and crystal lattice reorientation, which occur under conditions of the formation of nanostructural states [1–6], are controlled by cooperative deformation mechanisms. The cooperative character of deformation implies, on the one hand, collective behavior of elementary defects ensembles, which are deformation carriers, and, on the other hand, concurrent work of various modes of crystal deformation and reorientation, such as dislocation, disclination, and diffusion modes, mechanical twinning, and phase transformations. This paper briefly summarizes the results of a study of the role played by the mentioned cooperative mechanisms for the fragmentation of a crystal during the formation of nanostructural states in metal alloys (Cu, Ni, Ti, austenitic steels) and intermetallic compounds (Ni₃Al, TiNi) under various conditions of severe plastic deformation (SPD).