628 Journal of Personality Disorders, 26(4), 628–640, 2012 © 2012 The Guilford Press PSYCHOMETRIC EVALUATION OF THE BORDERLINE PERSONALITY DISORDER SEVERITY INDEX—IV—ADOLESCENT VERSION AND PARENT VERSION H. Marieke Schuppert, MD, Josephine Bloo, PhD, Ruud B. Minderaa, PhD, Paul M. G. Emmelkamp, PhD, and Maaike H. Nauta, PhD The Borderline Personality Disorder Severity Index–IV–adolescent and parent versions (BPDSI-IV-ado/p) are DSM-IV based semi-structured interviews for the assessment of the severity of symptoms of borderline personality disorder (BPD) in adolescents. The present study evaluates the psychometric properties of the BPDSI-IV-ado/p. The interviews were administered to 122 adolescents, aged 14–19 years and their par- ents/caretakers who were referred to mental health centres for emotion regulation problems, and to 45 healthy controls. The interrater reliabil- ity and internal consistency of all nine subscales (following the nine BPD symptoms in DSM-IV) proved to be good to excellent. Discrimi- nant, concurrent, and construct validity were satisfactory. Cut-off scores that optimize sensitivity and specificity were derived. Informant agreement between adolescents and parents/caretakers was modest. The results of this study suggest that the BPDSI-IV adolescent and par- ent versions are valid and reliable instruments for the assessment of BPD symptom severity in adolescents. Assessment and treatment of Borderline Personality Disorder (BPD) in ad- olescence have long been neglected, and many health professionals are hesitant in diagnosing BPD prior to age 18 (Crick, Murray-Close, & Woods, 2005). However, there is a growing body of evidence for a reliable and valid diagnosis of BPD in adolescence (Chanen, Jovev, et al., 2008; Johnson et al., 1999; Stepp, Pilkonis, Hipwell, Loeber, & Stouthamer-Loeber, 2010; Westen, Shedler, Durrett, Glass, & Martens, 2003). There is a need for a This article was accepted under the editorship of Paul S. Links. From University Medical Centre Groningen, the Netherlands (H. M. S., R. B. M., M. H. N.); University of Maastricht, the Netherlands (J. B.); and University of Amsterdam, the Nether- lands (P. M. G. E.). We acknowledge Marianne Hof, Evelien Miedema, Iris Rooke, Marjolein Schutte-Koning, and Annelies Wolters for their assistance in data collection. We thank all adolescents and parents who participated in the study. The study has been supported by ZonMW, the Netherlands organization for health research and development. Dutch Trial Register: NTR 984. Address correspondence to Marieke Schuppert, Child and Adolescent Psychiatrist, Accare, UCKJP, Postbox 660, 9700 AR Groningen, The Netherlands; E-mail: m.schuppert@accare.nl