This study examined the incremental validity of the Structured Interview for the Five-Factor Model (SIFFM; Trull & Widiger, 1997) scores in the prediction of borderline, antisocial, and histrionic personality disorder symptoms above and beyond variance accounted for by scores from the Schedule for Nonadaptive and Adaptive Personality (SNAP; Clark, 1993), a self-report questionnaire that includes items relevant to both normal (i.e. Big Three) and abnormal personality traits. Approximately 200 participants (52 clinical outpatients, and 149 nonclinical individuals from a borderline-features-enriched sample) completed the SIFFM, the SNAP, and select sections of the Personality Disorder Interview—IV (PDI-IV; Widiger, Mangine, Corbitt, Ellis, & Thomas, 1995). We found support for the incremental validity of SIFFM scores, further indicating the clinical utility of this instrument. However, results also supported the incremental validity of SNAP scores in many cases. We discuss the implications of the findings in terms of dimensional approaches to personality disorder assessment. Copyright © 2005 John Wiley & Sons, Ltd.