Recent discussion of proposed changes to the 5th version of the Diagnostic and Statistical Manual of Mental Disorders highlighted the struggle to categorize and define the characteristics of persons who present with Borderline Personality Disorder (BPD). BPD has traditionally been defined as a personality disorder, assuming a distinct trajectory and prognosis that sets it apart from other mood disorder diagnoses. However, early discussion in the development of the DSM-V introduced the possibility of BPD as one of several disorders existing on a shared mood disorder or emotion-regulation disorder spectrum. The final, published DSM-V retained BPD as a personality disorder on a diagnostic spectrum apart from mood or emotion regulation disorders; however, does BPD represent a broader and persistent difficulty with emotion regulation, rather than a disorder of the personality? In the current study, 73 psychiatric inpatients in a state-operated forensic hospital and 428 undergraduate students from a local university were administered the Difficulties in Emotion Regulation Scale (DERS), as well as the BPD section of the Structured Interview for the Diagnosis of Personality Disorders, DSM-IV version (SIDP-IV). Total and subscale scores on the DERS were correlated with individual symptom ratings from the SIDP-IV Borderline. Results suggest many of the subscales representing different facets of emotion regulation evidenced low to moderate correlations with symptoms of BPD. The subscales of the DERS least associated with symptoms and diagnosis of BPD are those that emphasize cognitive regulation of emotional experiences. Thus, it is likely that BPD would fit well within a conceptualization of emotion regulation disorder. Results also suggest some differences between groups, where more overlap between constructs exist for college students rather than psychiatric inpatients, with the least associated constructs are those that emphasize both cognitive and behavioral components of emotional regulation.