findings warrant reviewing the effects of oxytocin on cortisol in a larger sample than in previous studies. Using a 2×2 double-blind design, 100 healthy men received 24 I.U. of intranasal oxytocin or a saline placebo before participating in the Trier Social Stress Task (Kirschbaum et al., 1993) or a control procedure. Men who were given oxytocin and exposed to stress (the oxytocin/stress group) had significantly greater cortisol than the groupswhoonly received oxytocin or were only exposed to stress. The group difference in cortisol occurred in the absence of significant differences in selfreported state mood. However, the oxytocin/stress group reported higher trait neuroticism, which could increase stress-induced cortisol. When controlling neuroticism, the oxytocin/stress group still exhibited significantly greater cortisol. This is the first study to suggest that oxytocin may increase stress-induced cortisol in humans. One explanation for these results is that sufficient doses of oxytocin bind with receptors of the structurally similar hormone arginine vasopressin (AVP); AVP is known to synergize with CRH to cause ACTH release and increase cortisol. Future research to assess oxytocin and AVP receptor binding will benefit from the development of tools such as oxytocin radioligands for use in positron emission tomography imaging in humans.