Autoimmunization is understood as a type of immune reactions to the unchanged autoantigens only. Autoimmune processes can be subdivided into the physiological ("sanitary" and regulatory) and pathological ones. Physiological processes are of importance in supporting natural immunological tolerance while pathological processes develop on the basis of the physiological ones in presence of various defects of suppressive mechanisms of the immune system. Pathological processes are the basis of the autoimmune diseases and diseases with secondary autoimmune disturbances. The distinction between organo-specific and organo-nonspecific autoimmune diseases can be taken as their preliminary tentative classification.