A group of 135 inpatients with dissociative identity disorder was followed for 2 years to monitor treatment outcome. Method: Fifty-four of the patients were located and reassessed after a 2-year period through the use of the same self-report measures and structured clinical interviews that had been initially administered. Results: The patients showed marked improvement on Schneiderian first-rank symptoms, mood and anxiety disorders, dissociative symptoms, and somatization, with a significant decrease in the number of psychiatric medications prescribed. Patients who were treated to integration were significantly more improved than those who had not yet reached integration. Conclusions: These findings, although preliminary, provide empirical validation of previous clinical impressions that patients with dissociative identity disorder may respond well to treatment.