This study examined the diagnostic efficacy of the DSM-IV Borderline Personality Disorder (BPD) criteria. One hundred and thirty monolingual Spanish adults (90 males and 40 females) were assessed in an outpatient psychiatric and substance abuse clinic using a Spanish-language version of the DSM-IVPDs diagnostic interview.BPD diagnosis was determined by the best available assessment method. Diagnostic efficacy indices were calculated for all BPD criteria, for the entire study group, and for gender subgroups. Overall, the best exclusion criterion was emotional instability, while suicide or self-injury was the best diagnostic criterion and the best overall expected factor. These results were independent of gender, similar to those reported elsewhere in the literature, and useful for diagnostic system improvement.