This is an up-to-date, comprehensive reference manual. Its authors include seasoned practicing mental health professionals and doctoral psychology program faculty with over a century of combined clinical experience assessing and treating Borderline Personality Disorder. The book provides a history of conceptual models contributing to the definition and diagnosis of Borderline Personality Disorder, and explains the development and evolution of current diagnostic criteria in the Diagnostic and Statistical Manual of the American Psychiatric Association, Fifth Edition (DSM 5). Various theoretical models for conceptualising, assessing, and treating Borderline Personality Disorder are presented, including Psychoanalytic, Object Relations, Cognitive-Behavioral, Dialectical Behavior Therapy, Constructionist, Evidence-Based, and Biological perspectives. Differential diagnosis is discussed, with specific attention to trauma and its effects on personality functioning. The recent emergence of Borderline Personality Disorder into American mainstream media and culture is explored, including the stigma associated with the diagnosis and its potential effect on the person diagnosed, friends and family, and providers of care. Current conceptualisations of the Borderline Personality Disorder diagnosis are discussed, including the possibility that there might be more than one type of Borderline Personality Disorder. Future directions for research, conceptualisation, assessment and treatment of Borderline Personality Disorder are explored, including potential DSM changes. Borderline Personality Disorder is a useful resource for practicing mental health professionals, and a powerful and concise source of information for doctoral level psychology students.