This remarkable article demonstrates the repetitive occurrence of feelings of depersonalization and of derealization, and the relationship between these feelings and the transference. The special characteristics of these feelings, their genesis, and their evolution are described. The feelings occurred for the first time during treatment, and appeared only during the analytic sessions. The author traces the feelings to origins in castration fears, homosexual desires, and fears of the analyst's death wishes. Deeply repressed oral frustrations caused partial temporary loss of parts of the patient's ego. The patient progressed from severe ritualistic obsessive-compulsive behavior to the syndrome of depersonalization. The author concludes