1. Vasopressin and oxytocin have been measured in the neurohypophysis of rats which had either been given a 2% (w/v) NaCl solution to drink or been deprived of drinking water for up to 5 days.2. There was a progressive decrease in the vasopressin content of the glands in both groups; the rates of depletion were not significantly different.3. Oxytocin also decreased progressively in both groups but the glands from the ;saline-treated' rats contained less hormone than those from the ;water-deprived' animals.4. The differences in gland content of oxytocin could not be correlated with differences between the plasma osmolalities or sodium concentrations of the two groups.