An examination of Breuer's treatment of Anna O. illustrates some of the controversies surrounding the recent rise of case reports of multiple personality disorder. Anna O., the first patient of the cathartic method, psychoanalysis, and dynamic psychiatry, fits current criteria for multiple personality disorder. Breuer's treatment, however, may have contributed to her states of absence; the timing, type, and intensity of Breuer's interventions make it possible that he unwittingly encouraged and amplified Anna's dissociations, reified her ego fragments, and then explained Anna's symptoms with the pseudomemories and confabulations recovered from Anna while she was hypnotized. A review of Breuer's treatment highlights some of the controversial aspects of multiple personality disorder, specifically its possible vulnerability to iatrogenesis via suggestion and unconscious collusion and other factors. The current stance of some multiple personality disorder enthusiasts, opaque to their participation in interactions that may lead to certain patient productions, resembles the older psychoanalytic stance exemplified by the early Breuer and Freud. The dialectic of the therapist as a neutral observer versus as an influential participant continues to be a focus of controversy, both within psychoanalysis and psychotherapy and in the understandings of the etiology and treatment of multiple personality disorder.