In this article, applications of attachment theories to therapy for personality disorders, especially for borderline personality disorder, are discussed by reviewing previous studies and articles. Attachment distortions in infancy and toddlers are one of the risk factors for borderline personality disorder. The hypothesized etiological mechanism is that attachment-trauma causes children's representations to become disorganized, and this state of mind forms the base of the psychopathology in borderline patients. Two therapies in which the attachment theories are considered to be one of the theoretical backgrounds are mentalization-based therapy and infant-parent psychotherapy.
 Four points are discussed. First, many factors other than attachment, including genetics, have been reported to be involved in molding personality. Second, the importance of preventive approaches for personality disorders was noted. Third, from the attachment theorist's point of view, the "corrective attachment experience" by patients with therapists is the basis of therapy progression. Lastly, the concept "attachment-trauma" may be confused in clinical practice because the trauma in attachment-trauma is not the same as that in general psychiatry.
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