The predominant model of general personality structure is arguably the Five Factor Model (FFM), consisting of the 5 broad domains of neuroticism, extraversion, openness, agreeableness, and conscientiousness. A hypothesis of long-standing interest has been that personality disorders can be understood as extreme and/or maladaptive variants of the domains and facets of the FFM. This hypothesis has now been formally recognized within Diagnostic and Statistical Manual of Mental Disorders-Fifth Edition (DSM-5) Section III and within the proposal for the 11th edition of the World Health Organization's diagnostic manual. However, a notable feature of both proposals is that they are largely (albeit not exclusively) unipolar with respect to maladaptive personality structure. The purpose of the current article is to present theoretical and empirical support for the presence of maladaptivity at both poles of all 5 domains of the FFM. Discussed in particular are implications for assessment for this maladaptive personality structure. (PsycINFO Database Record (c) 2019 APA, all rights reserved).