ADRENAL 17-hydroxycorticosteroid (17-OHCS) secretion in response to insulin hypoglycaemia has been evaluated directly in anaesthetized1 and unanaesthetized2 dogs. As to the mechanism of insulin-induced adrenocortical secretion, Dury3 suggested from his experimental results that insulin hypoglycaemia resulted in an increase in adrenal medullary secretion, which induced the release of adrenocortical hormones. On the other hand, it was claimed by some authors that insulin-induced adrenocortical secretion was not dependent on the sympathoadreno-medullary activity4–6. In the experiments of Egdahl7 the adrenal medullary response to E. coli endotoxin was found to be abolished by the transection of the spinal cord at C7 and the adrenal 17-OHCS secretion in response to endotoxin was not affected by the spinal cord transection. He suggested that the adrenal cortical response to endotoxin was not dependent on the activity of the sympatho-adrenomedullary system. Thus it seems of interest to evaluate directly the adrenal 17-OHCS secretion in response to insulin in cord-sectioned dogs.