The role of perverse sexuality as an organizing influence in “multiple personality” is explored in this paper. Following a brief review of psychoanalytic thinking on sexual trauma and perversion, the author discusses his own views on dissociation and “multiple personality.” A clinical case is then presented in which transsexualism, homosexuality, and sadomasochistic heterosexual practices were manifested during altered ego states. Analysis of the transference revealed the centrality of sadomasochism in this patient. It is hypothesized that various perverse structures may be formed within these seemingly autonomous, amnestic states, in order to contain anxiety and encapsulate the aggression which resulted from early psychic trauma. Issues relating to diagnosis, countertransference, reconstruction, and psychoanalytic technique are discussed also.