We report here a pilot trial that mainly aimed to assess the endogenous secretion of oxytocin (OXT) in patients with Borderline personality disorder (BPD) and healthy controls. It is the first trial with BPD using salivary OXT and studying its reactivity in a natural setting and an experimental stress task. Compared to controls, patients with BPD showed lower variation of OXT in the natural setting and lower OXT reactivity during the stress task, contrasting to higher perceived stress and anger states. We confirm the feasibility of the protocol. Our results encourage the implementation of a larger trial to address specific hypotheses.