Five hypophysectomized dogs and six normal control dogs were subjected to hypoglycemic shock and the catechol amine output of their adrenal vein blood was measured. The experimental dogs showed a higher output of catechol amines, particularly of NE, both before and after insulin-induced hypoglycemia, than did the control animals. These findings may suggest that the pituitary gland has an inhibitory action on adrenal medullary secretion in dogs.