The control of adrenal functions by locally secreted neuropeptides or neurotransmitters is of great physiological importance. Vasopressin (VP) is one of these autocrine/paracrine regulators. We demonstrated by RT-PCR and perifusion experiments that rat and human adrenal medulla expressed and released vasopressin under basal conditions and under stimulation by acetylcholine. Intra-adrenal concentrations of VP may be sufficient to activate adrenal VP receptors. In the cortex, only the V1a receptor subtype has been detected. It triggered both steroid secretion and cortical growth. In the medulla, both V1a and V1b receptor subtypes were expressed. V1b receptors were mainly present on chromaffin cells and stimulated catecholamine secretion. The role of the V1a receptor remains unclear. Pathophysiological studies also revealed that human pheochromocytoma did not overexpress vasopressin receptors but might oversecrete vasopressin causing high plasma VP concentrations and elevated blood pressure.