Congestive heart failure (CHF) is characterized by fluid and water retention, which frequently is a therapeutic challenge. Most conventional diuretics act primarily as saluretics, i.e. they inhibit renal tubular electrolyte reabsorption, which due to osmotic pressure promotes excretion of isotonic fluid. Arginine vasopressin (AVP) via the V1A receptor vasoconstricts and via the V2 receptor promotes water reabsorption in the renal collecting duct by inserting aquaporin-2 water channels into the luminal membrane. Novel V2 receptor antagonists act as powerful aquaretics, i.e. they excrete free water. We review the pharmacology of non-selective V1A/V2 receptor antagonists and selective V2 receptor antagonists currently in clinical development.