The personality disorders as represented in the DSM-IV-TR (American Psychiatric Association 2000) and ICD-10 (World Health Organization 1992) classification systems are characterized by trait-like disturbances in emotion, cognition, and social function. As a group, they share the important commonalities of chronic course with early onset, relative preservation of intelligence, and absence of gross neurological deficit. In order to summarize the neurobiological literature, we have chosen a heuristic organization that emphasizes the location of "lesion" of personality disorder within neural networks mediating mental activity. This is opposed to a model that locates the lesion in personality, phenomenology (Siever and Davis 1991), or molecules. All of these are equally valid as heuristics. The advantage of this approach is that it allows a novel, useful reorganization of the existing database, characterized by a close relationship between the identified neurobiological abnormalities and a neurobiologically plausible brain-based model.