The treatment of borderline personality disorder (BPD) remains controversial. The authors have developed an evidence-based treatment program rooted in attachment theory that integrates research on constitutional factors with environmental influences. BPD is conceived of as a disorder in the self-structure brought about through environmentally induced distortion of psychological functioning, which decouples key mental processes necessary for interpersonal and social function. The primary mental function involved is mentalization, which is enfeebled by an absence of contingent and marked mirroring during development. Treatment strategies target mentalization in order to foster the development of stable internal representations, to aid the formation of a coherent sense of self, and to enable to borderline patient to form more secure relationships in which motivations of self and other are better understood. Destabilization of the self leads to emotional volatility, so treatment also needs to focus on identification and appropriate expression of affect. This article describes some of the techniques used to enhance mentalization within the context of group and individual psychotherapy. Targeting of current symptomatology and behavior is insufficient. Therapists need to retain their own ability to mentalize, maintain mental closeness, focus on current mental states, and avoid excessive use of conflict interpretation and metaphor while paying careful attention to the use of transference and countertransference.