This article presents circadian variation in salivary oxytocin levels in a sample of 91 female participants, including 47 healthy controls and 44 patients with borderline personality disorder (BPD). A significant increase in salivary oxytocin levels was observed between awakening and early afternoon. There were no significant group differences and no Group × Time interaction. These findings have implications for research conducted in the field and suggest the need to control for time of assessment, as done in studies assessing cortisol.