Although most acknowledge the possible influence of genetic, constitutional, neurobehavioral, and early developmental factors, clinicians disagree on which of these features is more important in determining the presence of borderline pathology in adults. Historically, the best formulated and most persuasive postulates regarding the etiology of the borderline syndrome have come from psychodynamic models of personality development that infer from the adult patients’ reconstructions of past experiences possible intra- and interpsychic models of separation-individuation and identity formation. It is likely that many etiologic hypotheses obtain and that there are multiple causes to the onset of BPD. (55 pp.)