A decrease of oxytocin and vasopressin content was observed in the hypothalamus and neurohypophysis of immobilized rats but not of those exposed to cold. In rats otherwise not treated, dopaminergic blockade due to haloperidol was followed by an increase of the vasopressin content in the neurohypophysis. In immobilized animals, the hypothalamic and neurohypophysial content of oxytocin decreased and could be further reduced by haloperidol. In contrast haloperidol prevented the decrease of the hypothalamic and neurohypophysial vasopressin under conditions of stress owing to immobilization. In cold-exposed animals, however, haloperidol did not affect the storage of neurohypophysial vasopressin and oxytocin. Thus, it may be supposed that the response of oxytocinergic and vasopressinergic neurones to stress is dependent on the kind of stressor; furthermore, the dopaminergic transmission seems to be involved in the functional regulation of these neurones under conditions of stress due to immobilization.