The feeling of depersonalization is due to withdrawal of cathexis from self-representation of the ego. A similar withdrawal from the object representation leads to a feeling of derealization. These are defenses against powerful id drives which are viewed as a threat to survival. A lengthy case report is presented in which identification with the images of unsatisfactory sado-masochistic parents led to castration anxiety and fear of abandonment. The patient actively defended against this by giving up the sadistic self-representation in the ego (through withdrawal of cathexis) leading to feelings of depersonalization. In the absence of suitable models for identification, self-representation within the ego may be achieved by identification with the image of one hated sadistic parent, while the object becomes imbued with the image of the other. Depending on the degree of regression and reaggressivization, the defensive symptoms of estrangement, depersonalization, derealization, and loss of identity may result.