Using rhesus monkeys, we studied the effects of a behavioral stress on plasma concentrations of adrenocorticotropin, oxytocin, and vasopressin. The stress resulted in significant increases in adrenocorticotropin and significant decreases in oxytocin concentrations. No significant changes were seen in vasopressin concentrations. To further explore the relationship between plasma oxytocin and pituitary-adrenal function, dexamethasone was administered to rhesus monkeys. This resulted in significant increases in plasma oxytocin concentrations, while adrenocorticotropin decreased.