In conscious Pekin ducks adapted either to fresh water or to hypertonic saline (1.9%) as drinking fluid, urinary excretion, salt gland secretion and the serum concentration of radioimmunoassayable arginine-vasotocin (AVT) were examined with regard to their afferent and central control. The experiments were carried out under conditions of water diuresis, osmotic diuresis or supraorbital salt gland secretion, which were induced by continuous infusions of appropriate solutions. Temporary bilateral vagus blockade caused rises in AVT serum concentration accompanied by antidiuresis in hydrated ducks and by inhibition of salt gland secretion in salt-stressed ducks. Rostral brainstem cooling caused decreases of AVT serum concentration and water diuresis in ducks under osmotic diuresis and reduction of AVT serum concentration and inhibition of salt gland secretion in salt-stressed ducks. Cerebral osmotic stimulation in hydrated ducks by intracarotid injection or by intracerebroventricular microinfusion of hypertonic NaCl solutions caused antidiuretic reactions associated with rises of AVT serum concentration.