RESUMEN
S.'s therapy demonstrates some of the ways in which countertransference interferes with therapy of a case presenting with multiple personalities. Fascination with S.'s alter personalities and the desire to prove their genuineness, made her therapist search for them and then repeatedly invoke their appearance. Part of the reason was his inexperience with such cases that induced him to "play it by the book," and use "personality-centered procedures" (looking for a different part, giving it a name, speaking to it, etc.) that have yet to be scientifically validated, instead of adhering to the basic principles of psychotherapy. At a deeper level, however, his excessive preoccupation with S.'s personalities was one kind of collusion with her resistance to deal with the focal issue of her sexual ambivalence. Proof of this resistance also surfaced later as a motivated shift of focus in therapy, and a weakening of the therapeutic alliance. By the time this was evident, sabotage of therapy had already occurred.