In birds, the endocrine control of salt and fluid homeostasis has functional characteristics similar to those found in other vertebrates, particularly mammals, and involves integration of several hormonal systems. Three of the most important systemic hormones are the peptides arginine vasotocin (AVT), the avian antidiuretic principal, angiotensin II (All) and atrial natriuretic peptide (ANP). The afferent control of these hormones has been fairly well defined, as have their target organ effects. In response to disturbances in the tonicity and/or volume of body fluids, AVT and AII have physiological actions that are designed to prevent extracellular fluid volume (ECFV) shrinkage, whereas ANP acts to reverse or minimize ECFV expansion, especially the vascular volume. The main site of action for AVT, All and ANP is the kidney, however, extrarenal effects can also be demonstrated, with one important example being the supraorbital salt secreting glands found in birds exposed to severe osmotic stresses. In addition, centrally mediated effects of blood-borne hormones, acting at areas lacking a blood-brain-barrier, may well be an important supplementary mechanism of action, particularly in the case of All. Information about the molecular physiology of AVT, All and ANP is minimal, so that our understanding of events at the receptor and post-receptor level is based primarily on analogies made with mammalian studies.