Dialectical Behaviour Therapy (DBT) is a cognitive behavioural treatment initially developed for adult women with a diagnosis of borderline personality disorder (BPD) and a history of chronic suicidal behaviour (Linehan, 1993a; 1993b). DBT was the first treatment for BPD to demonstrate its efficacy in a randomised controlled trial (Linehan , Armstrong, Suarez, Allmon & Heard, 1991). Adaptations of the treatment (Dimeff & Koerner, 2007) and further randomised trials followed this initial study. This paper provides an overview of the theoretical and philosophical foundations of DBT and how these inform the major treatment strategies. Next, structural aspects of the treatment are described, and how the treatment structure allows for the adaptation of the treatment to different clinical settings. Finally, the paper reviews research evidence for the efficacy and effectiveness of the treatment and considers future research directions. (Contains 1 table.)