Borderline personality disorder is assessed through a clinical interview and personality scales, supplemented by a psychiatric examination, physical examination and psychological tests if necessary. The psychiatric examination is used to understand the patient’s personal, family and treatment history; the physical examination and ancillary tests (e.g. brain imaging) are used to help rule out physical disorders; and psychological tests are used to rule out other psychiatric disorders or to confirm whether the personality disorder is co-morbid with a psychiatric disorder.