ObjectivesInterpersonal dysfunction is central to borderline personality disorder (BPD). Recent research has focused on the role of oxytocin (OT) in BPD, particularly regarding associations of OT activity with symptoms, genetic polymorphisms of the oxytocin receptor coding gene (OXTR) in BPD, and experimental modification of interpersonal core problems of patients with BPD such as hypervigilance towards threat detection, mistrust, and non-verbal behaviour during social interaction by intranasal application of OT. MethodsA literature (medline') review was performed using the keywords oxytocin' and borderline personality disorder'. Secondary literature on trauma and attachment in relation to OT was also considered relevant. ResultsTogether, findings suggest that in BPD OT is associated with enhanced defensive mechanisms and avoidance behaviour. Moreover, gene-environment interaction concerning polymorphic variations of the OXTR gene and childhood adversity in BPD suggests that these genes convey developmental flexibility or differential susceptibility' to environmental contingencies, whereby BPD resides at the poor outcome end of the spectrum. ConclusionsIn view of the conflicting literature, it needs to be studied carefully whether OT can serve as a therapeutic agent given adjunct to psychotherapy in BPD. More research about the role of OT is also required with regard to the prevention of the non-genetic intergenerational transmission of BPD. Clarifying the role of OT in BPD may also benefit from research in non-human animals targeting the interaction between early adversity and OT availability more directly. Practitioner points The study of oxytocin can contribute to the understanding of the neurobiology of borderline personality disorder. Oxytocin is critically involved in attachment security, and methylation of the oxytocin receptor may play a role in the epigenetic modulation of early adversity. The intranasal application of oxytocin may be a useful therapeutic adjunct to psychotherapy. Insecure attachment and childhood adversity may produce differential neurobiological effects on the oxytocinergic system in borderline personality disorder. There is insufficient knowledge of how oxytocin interacts with vasopressin, testosterone, dopamine, and serotonin, which are also important key players in the experience of social reward and stress responsivity. It is unclear whether or not oxytocin could be beneficial in preventing the intergenerational (non-genetic) transmission of borderline personality traits.