Objective: At present, the most frequently investigated psychosocial intervention for borderline personality disorder (BPD) is dialectical behavior therapy (DBT). We conducted a meta-analysis to examine the efficacy and long-term effectiveness of DBT. Method: Systematic bibliographic research was undertaken to find relevant literature from online databases (PubMed, PsycINFO, PsychSpider, Medline). We excluded studies in which patients with diagnoses other than BPD were treated, the treatment did not comprise all components specified in the DBT manual or in the suggestions for inpatient DBT programs, patients failed to be diagnosed according to the "Diagnostic and Statistical Manual of Mental Disorders", and the intervention group comprised fewer than 10 patients. Using a mixed-effect hierarchical modeling approach, we calculated global effect sizes and effect sizes for suicidal and self-injurious behaviors. Results: Calculations of postintervention global effect sizes were based on 16 studies. Of these, 8 were randomized controlled trials (RCTs), and 8 were neither randomized nor controlled (nRCT). The dropout rate was 27.3% pre- to posttreatment. A moderate global effect and a moderate effect size for suicidal and self-injurious behaviors were found, when including a moderator for RCTs with borderline-specific treatments. There was no evidence for the influence of other moderators (e.g., quality of studies, setting, duration of intervention). A small impairment was shown from posttreatment to follow-up, including 5 RCTs only. Conclusions: Future research should compare DBT with other active borderline-specific treatments that have also demonstrated their efficacy using several long-term follow-up assessment points. (Contains 1 table, 4 figures and 4 footnotes.)