Our understanding and treatment of borderline personality disorder (BPD) continue to evolve. These patients were originally conceptualized as having a particular type of intrapsychic organization. The prospect of being able to understand the internal organization of such patients helped encourage the enormous rise in therapeutic enthusiasm for long-term, intensive, psychoanalytically informed treatments for these patients. The construct was modified when it was redefined as a syndrome with reliably identifiable and discriminating criteria (see Table 53–1 for the DSM-IV-TR criteria). After the adoption of BPD in DSM-III (American Psychiatric Association 1980), the disorder became the subject of empirical study. The research showed that borderline patients frequently recover from the disorder and that such recovery usually involves multiple forms and episodes of treatment. Investigators repeatedly found that borderline patients have significant deficits in their ability to tolerate affects, impulses, and aloneness. From these observations, as well as more general changes in mental health services, the treatment approach of the earlier era, in which long-term intensive psychoanalytic therapies were considered necessary, has been greatly modified.