In the last decade, literature concerning gender and borderline personality disorder has aroused much controversy and little lightness. Recently, borderline personality disorder has been characterized as the "bad girl" of the psychiatric terms; this implies a bigger use of this diagnose in women and a biased gender in the identification of this disorder. The Diagnostic and Statistical Manual of Mental Disorders states that borderline personality disorder is mostly diagnosed in women (75%). The essential question to discuss is whether the larger prevalence in women is due to a biased sample or a biased diagnoses or it reflects a sociocultural and biological difference between men and women. The aim of this paper is to analyze some issues about the difference 3:1 women and men in this disorder.