Borderline Evaluation of Severity over Time  (BEST; Blum, Pfohl, John, Monahan, & Black, 2002). The BEST is a 15-item self-report measure assessing symptoms associated with borderline personality disorder (BPD) in adults.  The BEST can be used as a screening tool and diagnostic tool, and to monitor symptom change over time (Pfohl et al., 2009. The BEST has not been used with adolescents, nor does a separate adolescent version exist.  The measure consists of three subscales: thoughts and feelings, negative behaviors, and positive behaviors. Sample items include, “Feelings of emptiness,” “Going to extremes to try to keep someone from leaving you,” and “Choosing to use a positive activity in circumstances where you felt tempted to do something destructive or self-defeating.” All items on both the thoughts and feelings and negative behaviors subscales are rated on a 5-point scale from one (“none/slight”) to five (“extreme”). Items on the positive behaviors subscale are rated on a 5-poi