1. The characteristic response of the autotransplanted adrenal gland of the sheep to sodium depletion was an increase in aldosterone secretion rate, which reached the minimum detectable level of 1 μg/hr 6–12 hr after the Na balance became negative, when the Na deficit was approx. 200 m-equiv.
2. After its initial detection, aldosterone secretion altered in an irregular manner to maximum secretion rates of 5–9 μg/hr.
3. The initial detection of aldosterone secretion was not accompanied by any consistent changes in cortisol and corticosterone secretion.
4. Changes in cortisol and corticosterone secretion rates were usually in the same direction and of similar relative magnitude, and did not show any consistent correlation with the aldosterone secretion rates. The rates of cortisol and corticosterone secretion were extremely variable, but there was inconclusive evidence that there may have been a natural periodic variation of secretion rate, characteristic for individual sheep, which was modified by the experimental procedure.
5. The relationship between adrenal corticosteroid secretion and changes in blood plasma and urine electrolytes as well as haematocrit, plasma protein concentration and adrenal blood flow was examined.
6. Attention is drawn to the possible complexity of the relationship between adrenal corticosteroid secretion and the salivary Na/K ratio.