The etiology of borderline personality disorder (BPD) is an enigma. Recent reports have suggested that neuropsychiatric abnormalities play an important role in the etiology of this disorder. However, it has been difficult to judge the etiologic importance of these abnormalities because of the paucity of studies in this area. In this paper, we make a first comprehensive evaluation of the importance of these abnormalities in the etiology of BPD by assessing the presence of selected neuropsychological abnormalities in a sample of BPD patients and by reviewing our previously published data concerning neurodevelopmental abnormalities, EEG dysrhythmias, and family histories of neurological disorders in BPD patients versus controls. Our data suggest that the neuropsychiatric abnormalities that were studied are at most an uncommon etiology of this disorder.