On the basis of the information available at this time, it appears likely that the volume aspects of ADH (antidiuretic hormone) regulation is by a mechanism comparable to that for arterial pressure control, i. e., (a) the secretion of ADH is tonically stimulated by reticular formation activity just as is vasomotor sympathetic activity, and (b) the effect of vascular reflexes on ADH output is by virtue of inhibition either of the medullary-pontine reticular formation via internuncials arising in the nucleus solitarius or by ascending relays to the hypothalamus.