Borderline personality disorder (BPD) is a severe mental disorder that is associated with substantial psychosocial impairment and morbidity, disproportionate use of health resources, a high suicide rate, and a reputation for being "untreatable". A diagnosis of BPD in young people has similar reliability, validity and prevalence to BPD in adults, and almost certainly has serious and pervasive negative repercussions over subsequent decades. Current data are inadequate to inform specific universal or selective prevention programs for BPD. However, they do support including BPD prevention as an outcome when evaluating universal and/or selective interventions for a variety of mental health problems and adverse psychosocial outcomes. The strongest data support early intervention for the emerging BPD phenotype. Early intervention programs will need to be realistic in their aims, require change in clinician attitudes and service systems, and must be mindful of the risk of iatrogenic harm.