The past quarter century has seen the borderline personality disorder diagnosis (BPD) become the center of both controversy and creative endeavor in our field. Beginning with descriptions of a vaguely defined constellation of symptoms and dynamics, a literature has evolved that has gradually given us increasing clarity in our work as clinicians. BPD has been at the forefront in discussions about the widening scope of psychoanalysis, and the diagnosis has been misused as a countertransference response to difficult patients. However, within the vast literature about BPD is an accumulation of research data about the diagnosis and treatment of these patients, as well as studies of the origins