This is a commentary on Miller and Widiger’s (this volume) excellent chapter on personality disorders from the perspective of five factor personality models. In this commentary, the author discusses several issues of importance as the field moves forward with respect to dimensional personality-based diagnosis of personality disorder, most of which center on clinical application. First, a question is posed as to what level of personality abstraction is necessary for optimal formulation of personality disorders; although most five-factor models are established at the domain level, proposed personality disorder trait profiles appear at a much narrower facet level for which less scholarly consensus exist. Moreover, the author calls for more research into determining at what threshold on various trait dimensions clinical dysfunction begins to emerge. He also notes that most assessment devices currently available for dimensional trait models do not meet the Standards for Educational and Psychological Testing, which needs to be rectified prior to clinical application. Such tests also need to include validity scales to assess for noncredible responding. Finally, the author recommends that proposed personality inventories for these dimensional personality models show incremental utility above and beyond already well-established clinical assessment instruments.