A consistent picture of the evolution of the defect structure is presented for a solid undergoing plastic deformation, when defects are multiplied and arbitrary hierarchical structures are formed. The complete problem is reduced to a description of the kinetics of the formation of a new structural level of plastic deformation, a field-theoretic description of a single defect, and a statistical description of ensembles of defects. For the first time a theoretical scheme is constructed for the processes of developed plastic deformation in which a hierarchically connected multilevel structure of defects is formed. A solid with defects is treated as a highly nonequilibrium state of a crystal subjected to an intense external action.